chatserver/client.py

@@ -1,4 +1,3 @@
-import os
 import socket
 import sys
 import select
@@ -16,15 +15,6 @@ def main():
         SERVER_HOST = sys.argv[1]
         SERVER_PORT = int(sys.argv[2])
 
-    # Prompt user for a local directory path for file operations
-    while True:
-        local_path = input("Enter a local directory path for sending/receiving files: ").strip()
-        if os.path.isdir(local_path):
-            print(f"Using directory: {local_path}")
-            break
-        else:
-            print("Invalid directory. Please enter a valid path.")
-
     # create a socket object
     client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
     try:
@@ -32,13 +22,6 @@ def main():
         client_socket.connect((SERVER_HOST, SERVER_PORT))
         print(f"Connected to chat server at {SERVER_HOST}:{SERVER_PORT}")
         
-        # Prompt user for a username and send it to the server
-        username = input("Enter your username: ").strip()
-        client_socket.send(username.encode('utf-8'))
-
-        # Send the local path to the server
-        client_socket.send(f"SET_PATH {local_path}".encode('utf-8'))
-
         while True:
             # use select to wait for either server messages or user input
             read_sockets, _, _ = select.select([client_socket, sys.stdin], [], [])
@@ -50,43 +33,16 @@ def main():
                     if not server_message:
                         print("Disconnected from server")
                         return
-                    if server_message.startswith("FILE_REQUEST"):
-                        # Handle file request
-                        _, sending_username, filename = server_message.split()
-                        file_path = os.path.join(local_path, filename)
-                        if os.path.isfile(file_path):
-                            file_size = os.path.getsize(file_path)
-                            with open(file_path, "rb") as f:
-                                file_bytes = f.read()
-                            filetype = "File"
-                            client_socket.send(
-                                f"@{sending_username}@CLIENT -f {filename} {filetype} {file_size} {file_bytes.decode('latin1')} ENDFILE".encode('utf-8')
-                            )
-                        else:
-                            client_socket.send(
-                                f"@{sending_username}@CLIENT -f {filename} NOTFOUND".encode('utf-8')
-                            )
-                    elif server_message.startswith("FILE_TRANSFER"):
-                        # Handle file transfer
-                        _, sending_username, filename, filetype, filelength = server_message.split()
-                        file_bytes = client_socket.recv(int(filelength))
-                        end_marker = client_socket.recv(BUFFER_SIZE).decode('utf-8')
-                        if end_marker == "ENDFILE":
-                            file_path = os.path.join(local_path, filename)
-                            with open(file_path, "wb") as f:
-                                f.write(file_bytes)
-                            print(f"Received file '{filename}' from {sending_username}.")
-                    else:
                     print(f"\n{server_message}")
                     print("> ", end="", flush=True)
                 else:
-                    # Prompt for user input
+                    # prompt for user input
-                    client_message = input("> ").strip()
+                    client_message = input()
-                    if client_message == "%!":
+                    if client_message.strip() == "%!":
                         print("Exiting chat...")
                         return
                     
-                    # Send message to server
+                    # send message to server
                     client_socket.send(client_message.encode('utf-8'))
     
     except Exception as e:

chatserver/server.py

@@ -1,167 +1,138 @@
-import os
 import socket
 import select
-import threading
 
 CHATPORT = 8181
 BUFFER_SIZE = 1024
 MAX_CONNECT_QUEUE = 10
 
-def format_file_info(file_path):
+def main():
-    """Helper function to format file information."""
+    # set the flag variable to true for infinite loop
-    file_size = os.path.getsize(file_path)
+    quitFlag = True
-    if file_size < 1000:
+    # create a socket object
-        size_str = f"{file_size} B"
+    server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
-    elif file_size < 1000000:
+    # set the socket options, SO_REUSEADDR allows to reuse the same port
-        size_str = f"{file_size / 1000:.2f} KB"
+    # SO_KEEPALIVE enables the socket to send keepalive messages
+    server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+    server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1)
+    # bind the socket to the address and port
+    server_socket.bind(('', CHATPORT))
+    # listen for incoming connections
+    server_socket.listen(MAX_CONNECT_QUEUE)
+    # set the server socket to non-blocking
+    server_socket.setblocking(False)
+
+    # create a list to store the sockets, server and client
+    socket_list = [server_socket]
+    # since a socket is associated with a username and a chatroom, 
+    # and each one can only be associated one way at once, use dictionaries to
+    # associate with each other.
+    usernames = {}
+    chat_rooms = {}
+    # keep track of the states of each client connected, and if they are 
+    # technically in an 'unsafe' state like in change username or chatroom mode.
+    client_states = {}
+    # let the user know the server is listening on port CHATPORT.
+    print(f"Chatserver listening on port: {CHATPORT}")
+
+    # infinite loop for the program
+    while quitFlag:
+        # use the select function to monitor the sockets
+        read_sockets, _, _ = select.select(socket_list, [], [])
+        # loop through the sockets
+        for sock in read_sockets:
+            # if the socket is the server socket, accept the connection
+            if sock == server_socket:
+                client_socket, client_address = server_socket.accept()
+                client_socket.setblocking(False)
+                socket_list.append(client_socket)
+                print("\nAccepted connection from new client.")
+                client_socket.send(b"\nWelcome to the chat server!\n")
+                client_socket.send(b"\nUse '%!' to exit, or '%?' for help.\n")
+                client_socket.send(b"\nType in a username: ")
+                client_states[client_socket] = "WAITING_FOR_USERNAME"
+            # otherwise the socket is a client socket.
             else:
-        size_str = f"{file_size / 1000000:.2f} MB"
+                # try to receive the message from the client
-    file_type = "Directory" if os.path.isdir(file_path) else "File"
-    return f"{os.path.basename(file_path)} - {file_type} - {size_str}"
-
-def handle_client(sock, client_address, socket_list, usernames, chat_rooms, client_states, user_paths):
-    """Handle communication with a single client."""
                 try:
-        while True:
                     message = sock.recv(BUFFER_SIZE).decode('utf-8')
-            if not message:
+                    if message:
-                break
-
                         state = client_states.get(sock, "NORMAL")
                         if state == "WAITING_FOR_USERNAME":
-                # Handle username setup
                             usernames[sock] = message.strip()
                             chat_rooms[sock] = "default"
                             sock.send(b"\nUsername accepted. You are now in the 'default' chatroom.")
                             client_states[sock] = "NORMAL"
-                user_paths[sock] = None  # Initialize path for the user
+                        elif state == "WAITING_FOR_NEW_USERNAME":
-            elif state == "NORMAL":
+                            usernames[sock] = message.strip()
-                if message.startswith("SET_PATH"):
+                            sock.send(b"\nUsername changed successfully.")
-                    # Handle setting the user's directory path
+                            print(f"\nClient switched username to {usernames[sock]}.")
-                    _, path = message.split(" ", 1)
+                            client_states[sock] = "NORMAL"
-                    if os.path.isdir(path):
+                        elif state == "WAITING_FOR_NEW_CHATROOM":
-                        user_paths[sock] = path
+                            old_chatroom = chat_rooms[sock]
-                        sock.send(b"Directory path set successfully.")
+                            chat_rooms[sock] = message.strip()
+                            sock.send(f"\nSwitched to chatroom '{chat_rooms[sock]}.'".encode('utf-8'))
+                            print(f"\nClient switched to chatroom '{chat_rooms[sock]}.'")
+                            if old_chatroom != "default" and old_chatroom not in chat_rooms.values():
+                                print(f"\nChatroom '{old_chatroom}' is empty and removed.")
+                            client_states[sock] = "NORMAL"
                         else:
-                        sock.send(b"Error: Invalid directory path.")
+                            if message.strip() == "%!":
-                elif message.startswith("@") and "-ls" in message:
+                                sock.close()
-                    # Handle directory listing request
+                                socket_list.remove(sock)
-                    parts = message.split()
+                                del usernames[sock]
-                    if len(parts) == 2 and parts[1] == "-ls":
+                                del chat_rooms[sock]
-                        target_username = parts[0][1:]  # Extract the username after '@'
+                                del client_states[sock]
-                        target_sock = next((s for s, u in usernames.items() if u == target_username), None)
+                                print("\nClient has closed connection.")
-                        if target_sock:
+                            elif message.strip() == "%?":
-                            user_path = user_paths.get(target_sock)
+                                print("\nClient requested help.")
-                            if user_path and os.path.isdir(user_path):
+                                sock.send(b"Help: (%?)\n")
-                                files = os.listdir(user_path)
+                                sock.send(b"Send messages like normal. Use enter to send a message.\n")
-                                if files:
+                                sock.send(b"Available Commands:\n")
-                                    file_list = "\n".join(
+                                sock.send(b"\t%? : Show this help prompt.\n")
-                                        [format_file_info(os.path.join(user_path, f)) for f in files]
+                                sock.send(b"\t%! : Exit from the Chat Server.\n")
-                                    )
+                                sock.send(b"\t%* : Switch to another chatroom.\n")
-                                    sock.send(f"Files in {target_username}'s directory:\n{file_list}".encode('utf-8'))
+                                sock.send(b"\t%$ : Change Username.\n")
+                            elif message.strip() == "%*":
+                                sock.send(b"\nEnter chatroom name: ")
+                                client_states[sock] = "WAITING_FOR_NEW_CHATROOM"
+                            elif message.strip() == "%$":
+                                sock.send(b"\nEnter new username: ")
+                                client_states[sock] = "WAITING_FOR_NEW_USERNAME"
                             else:
-                                    sock.send(f"No files in {target_username}'s directory.".encode('utf-8'))
+                                username = usernames[sock]
-                            else:
+                                chat_room = chat_rooms[sock]
-                                sock.send(f"Error: {target_username} has no valid directory set.".encode('utf-8'))
-                        else:
-                            sock.send(b"Error: Target user not found.")
-                    else:
-                        sock.send(b"Error: Invalid message format.")
-                elif message.startswith("@") and "-f" in message:
-                    # Handle file request or transfer
-                    parts = message.split()
-                    if len(parts) >= 3 and "-f" in parts[1]:
-                        usernames_part = parts[0]
-                        if usernames_part.count("@") == 2:
-                            receiving_username, sending_username = usernames_part[1:].split("@")
-                            receiving_sock = next((s for s, u in usernames.items() if u == receiving_username), None)
-                            if receiving_sock:
-                                if len(parts) == 3:
-                                    # File request
-                                    filename = parts[2]
-                                    receiving_sock.send(f"FILE_REQUEST {sending_username} {filename}".encode('utf-8'))
-                                elif len(parts) > 5 and parts[-1] == "ENDFILE":
-                                    # File transfer
-                                    filename = parts[2]
-                                    filetype = parts[3]
-                                    filelength = int(parts[4])
-                                    filebytes = " ".join(parts[5:-1]).encode('utf-8')
-                                    receiving_sock.send(
-                                        f"FILE_TRANSFER {sending_username} {filename} {filetype} {filelength}".encode('utf-8')
-                                    )
-                                    receiving_sock.send(filebytes)
-                                    receiving_sock.send(b"ENDFILE")
-                            else:
-                                sock.send(b"Error: Receiving user not found.")
-                        else:
-                            sock.send(b"Error: Invalid message format.")
-                elif message.strip() == "%!":
-                    # Handle client exit
-                    break
-                else:
-                    # Broadcast message to other clients in the same chat room
-                    username = usernames.get(sock, "Unknown")
-                    chat_room = chat_rooms.get(sock, "default")
                                 send_message = f"{username} >> {message}".encode('utf-8')
                                 for client_sock in socket_list:
-                        if chat_rooms.get(client_sock) == chat_room:
+                                    if client_sock != server_socket and chat_rooms.get(client_sock) == chat_room:
-                            try:
                                         client_sock.send(send_message)
-                            except Exception as e:
+                    else:
-                                print(f"Error sending message to {client_sock}: {e}")
-                                client_sock.close()
-                                socket_list.remove(client_sock)
-    except Exception as e:
-        print(f"Error with client {client_address}: {e}")
-    finally:
-        # Clean up on client disconnect
                         sock.close()
                         socket_list.remove(sock)
                         if sock in usernames:
                             del usernames[sock]
                         if sock in chat_rooms:
+                            old_chatroom = chat_rooms[sock]
                             del chat_rooms[sock]
+                            if old_chatroom != "default" and old_chatroom not in chat_rooms.values():
+                                print(f"\nChatroom '{old_chatroom}' is empty and has been removed.")
                         if sock in client_states:
                             del client_states[sock]
-        if sock in user_paths:
+                        print("\nClient has closed connection.")
-            del user_paths[sock]
+                except Exception as err:
-        print(f"Client {client_address} disconnected.")
+                    print(f"Error: {err}")
+                    sock.close()
+                    socket_list.remove(sock)
+                    if sock in usernames:
+                        del usernames[sock]
+                    if sock in chat_rooms:
+                        old_chatroom = chat_rooms[sock]
+                        del chat_rooms[sock]
+                        if old_chatroom != "default" and old_chatroom not in chat_rooms.values():
+                            print(f"\nChatroom '{old_chatroom}' is empty and has been removed.")
+                    if sock in client_states:
+                        del client_states[sock]
+                    print("\nClient has closed connection.")
 
-def main():
-    # Initialize server
-    server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
-    server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
-    server_socket.bind(('', CHATPORT))
-    server_socket.listen(MAX_CONNECT_QUEUE)
-    print(f"Chatserver listening on port: {CHATPORT}")
-
-    # Shared data structures
-    socket_list = []
-    usernames = {}
-    chat_rooms = {}
-    client_states = {}
-    user_paths = {}
-
-    try:
-        while True:
-            client_socket, client_address = server_socket.accept()
-            print(f"Accepted connection from {client_address}")
-            socket_list.append(client_socket)
-
-            # Initialize client state
-            client_states[client_socket] = "WAITING_FOR_USERNAME"
-            user_paths[client_socket] = None
-
-            # Start a new thread for the client
-            client_thread = threading.Thread(
-                target=handle_client,
-                args=(client_socket, client_address, socket_list, usernames, chat_rooms, client_states, user_paths),
-                daemon=True
-            )
-            client_thread.start()
-    except KeyboardInterrupt:
-        print("\nShutting down server...")
-    finally:
     server_socket.close()
 
 if __name__ == "__main__":

echoserver/Makefile

@@ -0,0 +1,20 @@
+CC = gcc -Wall -std=c11 -pedantic
+SOURCES = echoserver.c 
+OBJECTS = echoserver.o 
+
+all: echoserver
+
+echoserver: $(OBJECTS)
+	$(CC) $(OBJECTS) -o echoserver
+
+echoserver.o: echoserver.c
+	$(CC) -c echoserver.c -o echoserver.o
+
+clean:
+	rm -f $(OBJECTS) echoserver echoserver.out
+
+clean_objects:
+	rm -f $(OBJECTS)
+
+run:
+	./echoserver

echoserver/README.md

@@ -0,0 +1,10 @@
+# Running the echoserver
+Use `make` to compile the echoserver.
+Use `make run` to run the echoserver. This will run on an infinite loop.
+Use `Ctrl+C` to stop the echoserver.
+
+## echoserver communication
+Communicating with the server can happen using telnet in TCP mode.
+
+## echoserver information
+The echoserver runs on TCP port 8888.

echoserver/echoserver.c

@@ -0,0 +1,150 @@
+// header files
+#include "echoserver.h"
+
+// constants
+// echoserver port is 8888
+#define ECHOPORT 8888
+#define BUFFER_SIZE 1024
+#define MAX_CONNECT_QUEUE 10
+
+// prototypes
+
+// main function
+int main(int argc, char **argv)
+{
+    // initialize program (variables and structs)
+    bool quitFlag = true;
+    int socketEchoFD;
+    int clientEchoFD;
+    int reuseAddrOpt = 1;
+    int keepAliveOpt = 1;
+    char message[BUFFER_SIZE];
+    int messageBytes;
+    struct sockaddr_in serverAddr;
+    struct sockaddr_storage clientAddr;
+    socklen_t clientSize;
+    memset(&serverAddr, 0, sizeof(serverAddr));
+    memset(&clientAddr, 0, sizeof(clientAddr));
+    // define a TCP socket
+    socketEchoFD = socket(AF_INET, SOCK_STREAM, 0);
+    if(socketEchoFD < 0)
+    {
+        printf("Unable to create the socket.\n");
+        return -1;
+    }
+    // use the setsockopt function to make the socket accept different configurations
+    // allow for the reuse of the address/bind.
+    setsockopt(socketEchoFD, SOL_SOCKET, SO_REUSEADDR, &reuseAddrOpt, sizeof(reuseAddrOpt));
+    // also need to set the socket to keepalive using setsockopt
+    setsockopt(socketEchoFD, SOL_SOCKET, SO_KEEPALIVE, &keepAliveOpt, sizeof(keepAliveOpt));
+    // bind the TCP socket to port 8888 / ECHOPORT
+    serverAddr.sin_family = AF_INET;
+    serverAddr.sin_addr.s_addr = INADDR_ANY;
+    serverAddr.sin_port = htons(ECHOPORT);
+    int bindCheck = bind(socketEchoFD, &serverAddr, sizeof(serverAddr));
+    if(bindCheck < 0)
+    {
+        printf("Unable to bind the socket to the port or address.\n Is either in use?");
+        return -1;
+    }
+    // use fnctl to set the non-blocking flag for the socket
+    fcntl(socketEchoFD, F_SETFL, O_NONBLOCK);
+    // the server will now accept client connections by listening.
+    listen(socketEchoFD, MAX_CONNECT_QUEUE);
+    // create a file descriptor set, to keep track of the sockets in use using fd_set and FD_ZERO?
+    fd_set socketList;
+    FD_ZERO(&socketList);
+    // add the socketEchoFD to the file descriptor set using fd_set
+    FD_SET(socketEchoFD, &socketList);
+    // max file descriptor, this will be used to 'find' the socket currently connected
+    int maxFD = socketEchoFD;
+    // while loop that will continue to listen for messages from clients.
+    printf("Echoserver listening on port: %d\n", ECHOPORT);
+    while (quitFlag)
+    {
+        // set of active connections
+        fd_set activeSet = socketList;
+        // use the select() function here to check the set of sockets
+        int selectedFD = select(maxFD+1, &activeSet, NULL, NULL, NULL);
+        // check to make sure select() didn't error out.
+        if(selectedFD == -1)
+        {
+            //
+            printf("\nUnable to select socket to listen to.\n");
+            return -1;
+        }
+        // for loop that loops up to the max file descriptor.
+        for(int fileIter = 0; fileIter <= maxFD; fileIter++)
+        {
+            // check to see if the file descriptor is in the set of sockets using FD_ISSET()
+            if(FD_ISSET(fileIter, &activeSet))
+            {
+                // if the server socket is being written to/read from,
+                if(fileIter == socketEchoFD)
+                {
+                    // create a client socket using accept
+                    clientSize = sizeof(clientAddr);
+                    clientEchoFD = accept(socketEchoFD, &clientAddr, &clientSize);
+                    // check to see if the client socket is connected (-1)
+                    if(clientEchoFD == -1)
+                    {
+                        printf("\nCould not connect the client to a socket.\n");
+                        return -1;
+                    }
+                    else
+                    {
+                        // set the non blocking flag using fnctl
+                        fcntl(clientEchoFD, F_SETFL, O_NONBLOCK);
+                        // add the client socket to the set of file descriptor sockets
+                        FD_SET(clientEchoFD, &socketList);
+                        // check to see if the new socket FD is greater than the current max (clientSocket > maxFD)
+                        if(clientEchoFD > maxFD)
+                        {
+                            // if it is, set the new max.
+                            maxFD = clientEchoFD;
+                        }
+                        printf("\nConnected client to socket.\n");
+                    }
+                    printf("\nAccepted connection from new client.\n");
+                }
+                // if the client socket(s) are being written to/read from,
+                else
+                {
+                    // grab the data from the client, save to message.
+                    messageBytes = recv(fileIter, message, BUFFER_SIZE, 0);
+                    // make sure that the connection is still open before attempting to send.
+                    if(messageBytes <= 0) // old: messageBytes <= 0
+                    {
+                        // if it is not open, close the socket and remove the socket from the socket list using FD_CLR()
+                        close(fileIter);
+                        FD_CLR(fileIter, &socketList);
+                        printf("\nClient has closed connection.\n");
+                    }
+                    else
+                    {
+                        // if it is open, send the message back to the client over the client socket
+                        send(fileIter, message, messageBytes, 0);
+                        printf("\nMessage has been sent back to client.\n");
+                    }
+                }
+            }
+        }
+    }
+    // close the socket
+    close(socketEchoFD);
+    // profit???
+    return 0;
+}
+
+// function definitions
+
+/*
+Name: ???
+Process: ???
+Function Input/Parameters: ???
+Function Output/Parameters: ???
+Function Output/Returned: ???
+Device Input/Device: ???
+Device Output/Device: ???
+Dependencies: ???
+*/

echoserver/echoserver.h

@@ -0,0 +1,25 @@
+#ifndef ECHOSERVER
+#define ECHOSERVER
+
+// included libraries
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+#include <stdbool.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/select.h>
+#include <netdb.h>
+#include <time.h>
+#include <unistd.h>
+#include <errno.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <fcntl.h>
+
+// data structures
+
+// function prototypes
+
+#endif // ECHOSERVER

networksim/README.md

@@ -0,0 +1,7 @@
+# Adapted tcp-variants-comparison file
+The `tcp-variants-comparison.cc` file has been adapted to allow for multiple TCP variants to be run in one simulation.
+In order to change the variants ran, find line 510-524. This is where the magic of which variants to run is.
+The code relies on multiple flows to also be ran, which can be found using the number of cases - 1. If you want to test the file, you'll want to replace the file with this modified version, which must then be rebuilt. You should be able to use `./ns3 build tcp-variants-comparison` (or `./ns3 build examples/tcp-variants-comparison` might work better) although this hasn't been tested, and the best method is to use ccache to cache the build before making the modification.
+
+## How to find the cwnd of multiple TCP variants (how to run)
+The command `./ns3 run tcp-variants-comparison --command-template="%s --tracing=1 --prefix_name=CS460Homework4_TCPCmp --num_flows=3 --access_delay=50ms"` can be used to find the comparisons between TCP variants. You'll want the number of flows to equal the amount of cases in the switch statement.

networksim/tcp-variants-comparison.cc

@@ -0,0 +1,624 @@
+/*
+ * Copyright (c) 2013 ResiliNets, ITTC, University of Kansas
+ *
+ * SPDX-License-Identifier: GPL-2.0-only
+ *
+ * Authors: Justin P. Rohrer, Truc Anh N. Nguyen <annguyen@ittc.ku.edu>, Siddharth Gangadhar
+ * <siddharth@ittc.ku.edu>
+ *
+ * James P.G. Sterbenz <jpgs@ittc.ku.edu>, director
+ * ResiliNets Research Group  https://resilinets.org/
+ * Information and Telecommunication Technology Center (ITTC)
+ * and Department of Electrical Engineering and Computer Science
+ * The University of Kansas Lawrence, KS USA.
+ *
+ * Work supported in part by NSF FIND (Future Internet Design) Program
+ * under grant CNS-0626918 (Postmodern Internet Architecture),
+ * NSF grant CNS-1050226 (Multilayer Network Resilience Analysis and Experimentation on GENI),
+ * US Department of Defense (DoD), and ITTC at The University of Kansas.
+ *
+ * "TCP Westwood(+) Protocol Implementation in ns-3"
+ * Siddharth Gangadhar, Trúc Anh Ngọc Nguyễn , Greeshma Umapathi, and James P.G. Sterbenz,
+ * ICST SIMUTools Workshop on ns-3 (WNS3), Cannes, France, March 2013
+ */
+
+#include "ns3/applications-module.h"
+#include "ns3/core-module.h"
+#include "ns3/enum.h"
+#include "ns3/error-model.h"
+#include "ns3/event-id.h"
+#include "ns3/flow-monitor-helper.h"
+#include "ns3/internet-module.h"
+#include "ns3/ipv4-global-routing-helper.h"
+#include "ns3/network-module.h"
+#include "ns3/point-to-point-module.h"
+#include "ns3/tcp-header.h"
+#include "ns3/traffic-control-module.h"
+#include "ns3/udp-header.h"
+
+#include <fstream>
+#include <iostream>
+#include <string>
+
+using namespace ns3;
+
+NS_LOG_COMPONENT_DEFINE("TcpVariantsComparison");
+
+static std::map<uint32_t, bool> firstCwnd;                      //!< First congestion window.
+static std::map<uint32_t, bool> firstSshThr;                    //!< First SlowStart threshold.
+static std::map<uint32_t, bool> firstRtt;                       //!< First RTT.
+static std::map<uint32_t, bool> firstRto;                       //!< First RTO.
+static std::map<uint32_t, Ptr<OutputStreamWrapper>> cWndStream; //!< Congstion window output stream.
+static std::map<uint32_t, Ptr<OutputStreamWrapper>>
+    ssThreshStream; //!< SlowStart threshold output stream.
+static std::map<uint32_t, Ptr<OutputStreamWrapper>> rttStream;      //!< RTT output stream.
+static std::map<uint32_t, Ptr<OutputStreamWrapper>> rtoStream;      //!< RTO output stream.
+static std::map<uint32_t, Ptr<OutputStreamWrapper>> nextTxStream;   //!< Next TX output stream.
+static std::map<uint32_t, Ptr<OutputStreamWrapper>> nextRxStream;   //!< Next RX output stream.
+static std::map<uint32_t, Ptr<OutputStreamWrapper>> inFlightStream; //!< In flight output stream.
+static std::map<uint32_t, uint32_t> cWndValue;                      //!< congestion window value.
+static std::map<uint32_t, uint32_t> ssThreshValue;                  //!< SlowStart threshold value.
+
+/**
+ * Get the Node Id From Context.
+ *
+ * @param context The context.
+ * @return the node ID.
+ */
+static uint32_t
+GetNodeIdFromContext(std::string context)
+{
+    const std::size_t n1 = context.find_first_of('/', 1);
+    const std::size_t n2 = context.find_first_of('/', n1 + 1);
+    return std::stoul(context.substr(n1 + 1, n2 - n1 - 1));
+}
+
+/**
+ * Congestion window tracer.
+ *
+ * @param context The context.
+ * @param oldval Old value.
+ * @param newval New value.
+ */
+static void
+CwndTracer(std::string context, uint32_t oldval, uint32_t newval)
+{
+    uint32_t nodeId = GetNodeIdFromContext(context);
+
+    if (firstCwnd[nodeId])
+    {
+        *cWndStream[nodeId]->GetStream() << "0.0 " << oldval << std::endl;
+        firstCwnd[nodeId] = false;
+    }
+    *cWndStream[nodeId]->GetStream() << Simulator::Now().GetSeconds() << " " << newval << std::endl;
+    cWndValue[nodeId] = newval;
+
+    if (!firstSshThr[nodeId])
+    {
+        *ssThreshStream[nodeId]->GetStream()
+            << Simulator::Now().GetSeconds() << " " << ssThreshValue[nodeId] << std::endl;
+    }
+}
+
+/**
+ * Slow start threshold tracer.
+ *
+ * @param context The context.
+ * @param oldval Old value.
+ * @param newval New value.
+ */
+static void
+SsThreshTracer(std::string context, uint32_t oldval, uint32_t newval)
+{
+    uint32_t nodeId = GetNodeIdFromContext(context);
+
+    if (firstSshThr[nodeId])
+    {
+        *ssThreshStream[nodeId]->GetStream() << "0.0 " << oldval << std::endl;
+        firstSshThr[nodeId] = false;
+    }
+    *ssThreshStream[nodeId]->GetStream()
+        << Simulator::Now().GetSeconds() << " " << newval << std::endl;
+    ssThreshValue[nodeId] = newval;
+
+    if (!firstCwnd[nodeId])
+    {
+        *cWndStream[nodeId]->GetStream()
+            << Simulator::Now().GetSeconds() << " " << cWndValue[nodeId] << std::endl;
+    }
+}
+
+/**
+ * RTT tracer.
+ *
+ * @param context The context.
+ * @param oldval Old value.
+ * @param newval New value.
+ */
+static void
+RttTracer(std::string context, Time oldval, Time newval)
+{
+    uint32_t nodeId = GetNodeIdFromContext(context);
+
+    if (firstRtt[nodeId])
+    {
+        *rttStream[nodeId]->GetStream() << "0.0 " << oldval.GetSeconds() << std::endl;
+        firstRtt[nodeId] = false;
+    }
+    *rttStream[nodeId]->GetStream()
+        << Simulator::Now().GetSeconds() << " " << newval.GetSeconds() << std::endl;
+}
+
+/**
+ * RTO tracer.
+ *
+ * @param context The context.
+ * @param oldval Old value.
+ * @param newval New value.
+ */
+static void
+RtoTracer(std::string context, Time oldval, Time newval)
+{
+    uint32_t nodeId = GetNodeIdFromContext(context);
+
+    if (firstRto[nodeId])
+    {
+        *rtoStream[nodeId]->GetStream() << "0.0 " << oldval.GetSeconds() << std::endl;
+        firstRto[nodeId] = false;
+    }
+    *rtoStream[nodeId]->GetStream()
+        << Simulator::Now().GetSeconds() << " " << newval.GetSeconds() << std::endl;
+}
+
+/**
+ * Next TX tracer.
+ *
+ * @param context The context.
+ * @param old Old sequence number.
+ * @param nextTx Next sequence number.
+ */
+static void
+NextTxTracer(std::string context, SequenceNumber32 old [[maybe_unused]], SequenceNumber32 nextTx)
+{
+    uint32_t nodeId = GetNodeIdFromContext(context);
+
+    *nextTxStream[nodeId]->GetStream()
+        << Simulator::Now().GetSeconds() << " " << nextTx << std::endl;
+}
+
+/**
+ * In-flight tracer.
+ *
+ * @param context The context.
+ * @param old Old value.
+ * @param inFlight In flight value.
+ */
+static void
+InFlightTracer(std::string context, uint32_t old [[maybe_unused]], uint32_t inFlight)
+{
+    uint32_t nodeId = GetNodeIdFromContext(context);
+
+    *inFlightStream[nodeId]->GetStream()
+        << Simulator::Now().GetSeconds() << " " << inFlight << std::endl;
+}
+
+/**
+ * Next RX tracer.
+ *
+ * @param context The context.
+ * @param old Old sequence number.
+ * @param nextRx Next sequence number.
+ */
+static void
+NextRxTracer(std::string context, SequenceNumber32 old [[maybe_unused]], SequenceNumber32 nextRx)
+{
+    uint32_t nodeId = GetNodeIdFromContext(context);
+
+    *nextRxStream[nodeId]->GetStream()
+        << Simulator::Now().GetSeconds() << " " << nextRx << std::endl;
+}
+
+/**
+ * Congestion window trace connection.
+ *
+ * @param cwnd_tr_file_name Congestion window trace file name.
+ * @param nodeId Node ID.
+ */
+static void
+TraceCwnd(std::string cwnd_tr_file_name, uint32_t nodeId)
+{
+    AsciiTraceHelper ascii;
+    cWndStream[nodeId] = ascii.CreateFileStream(cwnd_tr_file_name);
+    Config::Connect("/NodeList/" + std::to_string(nodeId) +
+                        "/$ns3::TcpL4Protocol/SocketList/0/CongestionWindow",
+                    MakeCallback(&CwndTracer));
+}
+
+/**
+ * Slow start threshold trace connection.
+ *
+ * @param ssthresh_tr_file_name Slow start threshold trace file name.
+ * @param nodeId Node ID.
+ */
+static void
+TraceSsThresh(std::string ssthresh_tr_file_name, uint32_t nodeId)
+{
+    AsciiTraceHelper ascii;
+    ssThreshStream[nodeId] = ascii.CreateFileStream(ssthresh_tr_file_name);
+    Config::Connect("/NodeList/" + std::to_string(nodeId) +
+                        "/$ns3::TcpL4Protocol/SocketList/0/SlowStartThreshold",
+                    MakeCallback(&SsThreshTracer));
+}
+
+/**
+ * RTT trace connection.
+ *
+ * @param rtt_tr_file_name RTT trace file name.
+ * @param nodeId Node ID.
+ */
+static void
+TraceRtt(std::string rtt_tr_file_name, uint32_t nodeId)
+{
+    AsciiTraceHelper ascii;
+    rttStream[nodeId] = ascii.CreateFileStream(rtt_tr_file_name);
+    Config::Connect("/NodeList/" + std::to_string(nodeId) + "/$ns3::TcpL4Protocol/SocketList/0/RTT",
+                    MakeCallback(&RttTracer));
+}
+
+/**
+ * RTO trace connection.
+ *
+ * @param rto_tr_file_name RTO trace file name.
+ * @param nodeId Node ID.
+ */
+static void
+TraceRto(std::string rto_tr_file_name, uint32_t nodeId)
+{
+    AsciiTraceHelper ascii;
+    rtoStream[nodeId] = ascii.CreateFileStream(rto_tr_file_name);
+    Config::Connect("/NodeList/" + std::to_string(nodeId) + "/$ns3::TcpL4Protocol/SocketList/0/RTO",
+                    MakeCallback(&RtoTracer));
+}
+
+/**
+ * Next TX trace connection.
+ *
+ * @param next_tx_seq_file_name Next TX trace file name.
+ * @param nodeId Node ID.
+ */
+static void
+TraceNextTx(std::string& next_tx_seq_file_name, uint32_t nodeId)
+{
+    AsciiTraceHelper ascii;
+    nextTxStream[nodeId] = ascii.CreateFileStream(next_tx_seq_file_name);
+    Config::Connect("/NodeList/" + std::to_string(nodeId) +
+                        "/$ns3::TcpL4Protocol/SocketList/0/NextTxSequence",
+                    MakeCallback(&NextTxTracer));
+}
+
+/**
+ * In flight trace connection.
+ *
+ * @param in_flight_file_name In flight trace file name.
+ * @param nodeId Node ID.
+ */
+static void
+TraceInFlight(std::string& in_flight_file_name, uint32_t nodeId)
+{
+    AsciiTraceHelper ascii;
+    inFlightStream[nodeId] = ascii.CreateFileStream(in_flight_file_name);
+    Config::Connect("/NodeList/" + std::to_string(nodeId) +
+                        "/$ns3::TcpL4Protocol/SocketList/0/BytesInFlight",
+                    MakeCallback(&InFlightTracer));
+}
+
+/**
+ * Next RX trace connection.
+ *
+ * @param next_rx_seq_file_name Next RX trace file name.
+ * @param nodeId Node ID.
+ */
+static void
+TraceNextRx(std::string& next_rx_seq_file_name, uint32_t nodeId)
+{
+    AsciiTraceHelper ascii;
+    nextRxStream[nodeId] = ascii.CreateFileStream(next_rx_seq_file_name);
+    Config::Connect("/NodeList/" + std::to_string(nodeId) +
+                        "/$ns3::TcpL4Protocol/SocketList/1/RxBuffer/NextRxSequence",
+                    MakeCallback(&NextRxTracer));
+}
+
+int
+main(int argc, char* argv[])
+{
+    std::string transport_prot = "TcpWestwoodPlus";
+    double error_p = 0.0;
+    std::string bandwidth = "2Mbps";
+    std::string delay = "0.01ms";
+    std::string access_bandwidth = "10Mbps";
+    std::string access_delay = "45ms";
+    bool tracing = false;
+    std::string prefix_file_name = "TcpVariantsComparison";
+    uint64_t data_mbytes = 0;
+    uint32_t mtu_bytes = 400;
+    uint16_t num_flows = 1;
+    double duration = 100.0;
+    uint32_t run = 0;
+    bool flow_monitor = false;
+    bool pcap = false;
+    bool sack = true;
+    std::string queue_disc_type = "ns3::PfifoFastQueueDisc";
+    std::string recovery = "ns3::TcpClassicRecovery";
+
+    CommandLine cmd(__FILE__);
+    cmd.AddValue("transport_prot",
+                 "Transport protocol to use: TcpNewReno, TcpLinuxReno, "
+                 "TcpHybla, TcpHighSpeed, TcpHtcp, TcpVegas, TcpScalable, TcpVeno, "
+                 "TcpBic, TcpYeah, TcpIllinois, TcpWestwoodPlus, TcpLedbat, "
+                 "TcpLp, TcpDctcp, TcpCubic, TcpBbr",
+                 transport_prot);
+    cmd.AddValue("error_p", "Packet error rate", error_p);
+    cmd.AddValue("bandwidth", "Bottleneck bandwidth", bandwidth);
+    cmd.AddValue("delay", "Bottleneck delay", delay);
+    cmd.AddValue("access_bandwidth", "Access link bandwidth", access_bandwidth);
+    cmd.AddValue("access_delay", "Access link delay", access_delay);
+    cmd.AddValue("tracing", "Flag to enable/disable tracing", tracing);
+    cmd.AddValue("prefix_name", "Prefix of output trace file", prefix_file_name);
+    cmd.AddValue("data", "Number of Megabytes of data to transmit", data_mbytes);
+    cmd.AddValue("mtu", "Size of IP packets to send in bytes", mtu_bytes);
+    cmd.AddValue("num_flows", "Number of flows", num_flows);
+    cmd.AddValue("duration", "Time to allow flows to run in seconds", duration);
+    cmd.AddValue("run", "Run index (for setting repeatable seeds)", run);
+    cmd.AddValue("flow_monitor", "Enable flow monitor", flow_monitor);
+    cmd.AddValue("pcap_tracing", "Enable or disable PCAP tracing", pcap);
+    cmd.AddValue("queue_disc_type",
+                 "Queue disc type for gateway (e.g. ns3::CoDelQueueDisc)",
+                 queue_disc_type);
+    cmd.AddValue("sack", "Enable or disable SACK option", sack);
+    cmd.AddValue("recovery", "Recovery algorithm type to use (e.g., ns3::TcpPrrRecovery", recovery);
+    cmd.Parse(argc, argv);
+
+    transport_prot = std::string("ns3::") + transport_prot;
+
+    SeedManager::SetSeed(1);
+    SeedManager::SetRun(run);
+
+    // User may find it convenient to enable logging
+    // LogComponentEnable("TcpVariantsComparison", LOG_LEVEL_ALL);
+    // LogComponentEnable("BulkSendApplication", LOG_LEVEL_INFO);
+    // LogComponentEnable("PfifoFastQueueDisc", LOG_LEVEL_ALL);
+
+    // Calculate the ADU size
+    Header* temp_header = new Ipv4Header();
+    uint32_t ip_header = temp_header->GetSerializedSize();
+    NS_LOG_LOGIC("IP Header size is: " << ip_header);
+    delete temp_header;
+    temp_header = new TcpHeader();
+    uint32_t tcp_header = temp_header->GetSerializedSize();
+    NS_LOG_LOGIC("TCP Header size is: " << tcp_header);
+    delete temp_header;
+    uint32_t tcp_adu_size = mtu_bytes - 20 - (ip_header + tcp_header);
+    NS_LOG_LOGIC("TCP ADU size is: " << tcp_adu_size);
+
+    // Set the simulation start and stop time
+    double start_time = 0.1;
+    double stop_time = start_time + duration;
+
+    // 2 MB of TCP buffer
+    Config::SetDefault("ns3::TcpSocket::RcvBufSize", UintegerValue(1 << 21));
+    Config::SetDefault("ns3::TcpSocket::SndBufSize", UintegerValue(1 << 21));
+    Config::SetDefault("ns3::TcpSocketBase::Sack", BooleanValue(sack));
+
+    Config::SetDefault("ns3::TcpL4Protocol::RecoveryType",
+                       TypeIdValue(TypeId::LookupByName(recovery)));
+    // Select TCP variant
+    TypeId tcpTid;
+    NS_ABORT_MSG_UNLESS(TypeId::LookupByNameFailSafe(transport_prot, &tcpTid),
+                        "TypeId " << transport_prot << " not found");
+    Config::SetDefault("ns3::TcpL4Protocol::SocketType",
+                       TypeIdValue(TypeId::LookupByName(transport_prot)));
+
+    // Create gateways, sources, and sinks
+    NodeContainer gateways;
+    gateways.Create(1);
+    NodeContainer sources;
+    sources.Create(num_flows);
+    NodeContainer sinks;
+    sinks.Create(num_flows);
+
+    // Configure the error model
+    // Here we use RateErrorModel with packet error rate
+    Ptr<UniformRandomVariable> uv = CreateObject<UniformRandomVariable>();
+    uv->SetStream(50);
+    RateErrorModel error_model;
+    error_model.SetRandomVariable(uv);
+    error_model.SetUnit(RateErrorModel::ERROR_UNIT_PACKET);
+    error_model.SetRate(error_p);
+
+    PointToPointHelper UnReLink;
+    UnReLink.SetDeviceAttribute("DataRate", StringValue(bandwidth));
+    UnReLink.SetChannelAttribute("Delay", StringValue(delay));
+    UnReLink.SetDeviceAttribute("ReceiveErrorModel", PointerValue(&error_model));
+
+    InternetStackHelper stack;
+    stack.InstallAll();
+
+    TrafficControlHelper tchPfifo;
+    tchPfifo.SetRootQueueDisc("ns3::PfifoFastQueueDisc");
+
+    TrafficControlHelper tchCoDel;
+    tchCoDel.SetRootQueueDisc("ns3::CoDelQueueDisc");
+
+    Ipv4AddressHelper address;
+    address.SetBase("10.0.0.0", "255.255.255.0");
+
+    // Configure the sources and sinks net devices
+    // and the channels between the sources/sinks and the gateways
+    PointToPointHelper LocalLink;
+    LocalLink.SetDeviceAttribute("DataRate", StringValue(access_bandwidth));
+    LocalLink.SetChannelAttribute("Delay", StringValue(access_delay));
+
+    Ipv4InterfaceContainer sink_interfaces;
+
+    DataRate access_b(access_bandwidth);
+    DataRate bottle_b(bandwidth);
+    Time access_d(access_delay);
+    Time bottle_d(delay);
+
+    uint32_t size = static_cast<uint32_t>((std::min(access_b, bottle_b).GetBitRate() / 8) *
+                                          ((access_d + bottle_d) * 2).GetSeconds());
+
+    Config::SetDefault("ns3::PfifoFastQueueDisc::MaxSize",
+                       QueueSizeValue(QueueSize(QueueSizeUnit::PACKETS, size / mtu_bytes)));
+    Config::SetDefault("ns3::CoDelQueueDisc::MaxSize",
+                       QueueSizeValue(QueueSize(QueueSizeUnit::BYTES, size)));
+
+    for (uint32_t i = 0; i < num_flows; i++)
+    {
+        NetDeviceContainer devices;
+        devices = LocalLink.Install(sources.Get(i), gateways.Get(0));
+        tchPfifo.Install(devices);
+        address.NewNetwork();
+        Ipv4InterfaceContainer interfaces = address.Assign(devices);
+
+        devices = UnReLink.Install(gateways.Get(0), sinks.Get(i));
+        if (queue_disc_type == "ns3::PfifoFastQueueDisc")
+        {
+            tchPfifo.Install(devices);
+        }
+        else if (queue_disc_type == "ns3::CoDelQueueDisc")
+        {
+            tchCoDel.Install(devices);
+        }
+        else
+        {
+            NS_FATAL_ERROR("Queue not recognized. Allowed values are ns3::CoDelQueueDisc or "
+                           "ns3::PfifoFastQueueDisc");
+        }
+        address.NewNetwork();
+        interfaces = address.Assign(devices);
+        sink_interfaces.Add(interfaces.Get(1));
+    }
+
+    NS_LOG_INFO("Initialize Global Routing.");
+    Ipv4GlobalRoutingHelper::PopulateRoutingTables();
+
+    uint16_t port = 50000;
+    Address sinkLocalAddress(InetSocketAddress(Ipv4Address::GetAny(), port));
+    PacketSinkHelper sinkHelper("ns3::TcpSocketFactory", sinkLocalAddress);
+
+    for (uint32_t i = 0; i < sources.GetN(); i++)
+    {
+        // Assign a different TCP variant to each flow
+        std::string tcpVariant;
+        switch (i % 2) // Example: Rotate between two TCP variants
+        {
+        case 0:
+            tcpVariant = "ns3::TcpNewReno";
+            break;
+        case 1:
+            tcpVariant = "ns3::TcpCubic";
+            break;
+        default:
+            tcpVariant = "ns3::TcpNewReno";
+        }
+
+        // Set the TCP variant for this flow
+        Config::Set("/NodeList/" + std::to_string(sources.Get(i)->GetId()) +
+                        "/$ns3::TcpL4Protocol/SocketType",
+                    StringValue(tcpVariant));
+
+        // Configure the BulkSend application
+        Address remoteAddress(InetSocketAddress(sink_interfaces.GetAddress(i, 0), port));
+        BulkSendHelper ftp("ns3::TcpSocketFactory", remoteAddress);
+        ftp.SetAttribute("SendSize", UintegerValue(tcp_adu_size));
+        ftp.SetAttribute("MaxBytes", UintegerValue(data_mbytes * 1000000));
+
+        ApplicationContainer sourceApp = ftp.Install(sources.Get(i));
+        sourceApp.Start(Seconds(start_time * i));
+        sourceApp.Stop(Seconds(stop_time - 3));
+
+        // Configure the PacketSink application
+        sinkHelper.SetAttribute("Protocol", TypeIdValue(TcpSocketFactory::GetTypeId()));
+        ApplicationContainer sinkApp = sinkHelper.Install(sinks.Get(i));
+        sinkApp.Start(Seconds(start_time * i));
+        sinkApp.Stop(Seconds(stop_time));
+    }
+
+    // Set up tracing if enabled
+    if (tracing)
+    {
+        std::ofstream ascii;
+        Ptr<OutputStreamWrapper> ascii_wrap;
+        ascii.open(prefix_file_name + "-ascii");
+        ascii_wrap = new OutputStreamWrapper(prefix_file_name + "-ascii", std::ios::out);
+        stack.EnableAsciiIpv4All(ascii_wrap);
+
+        for (uint16_t index = 0; index < num_flows; index++)
+        {
+            std::string flowString;
+            if (num_flows > 1)
+            {
+                flowString = "-flow" + std::to_string(index);
+            }
+
+            firstCwnd[index + 1] = true;
+            firstSshThr[index + 1] = true;
+            firstRtt[index + 1] = true;
+            firstRto[index + 1] = true;
+
+            Simulator::Schedule(Seconds(start_time * index + 0.00001),
+                                &TraceCwnd,
+                                prefix_file_name + flowString + "-cwnd.data",
+                                index + 1);
+            Simulator::Schedule(Seconds(start_time * index + 0.00001),
+                                &TraceSsThresh,
+                                prefix_file_name + flowString + "-ssth.data",
+                                index + 1);
+            Simulator::Schedule(Seconds(start_time * index + 0.00001),
+                                &TraceRtt,
+                                prefix_file_name + flowString + "-rtt.data",
+                                index + 1);
+            Simulator::Schedule(Seconds(start_time * index + 0.00001),
+                                &TraceRto,
+                                prefix_file_name + flowString + "-rto.data",
+                                index + 1);
+            Simulator::Schedule(Seconds(start_time * index + 0.00001),
+                                &TraceNextTx,
+                                prefix_file_name + flowString + "-next-tx.data",
+                                index + 1);
+            Simulator::Schedule(Seconds(start_time * index + 0.00001),
+                                &TraceInFlight,
+                                prefix_file_name + flowString + "-inflight.data",
+                                index + 1);
+            Simulator::Schedule(Seconds(start_time * index + 0.1),
+                                &TraceNextRx,
+                                prefix_file_name + flowString + "-next-rx.data",
+                                num_flows + index + 1);
+        }
+    }
+
+    if (pcap)
+    {
+        UnReLink.EnablePcapAll(prefix_file_name, true);
+        LocalLink.EnablePcapAll(prefix_file_name, true);
+    }
+
+    // Flow monitor
+    FlowMonitorHelper flowHelper;
+    if (flow_monitor)
+    {
+        flowHelper.InstallAll();
+    }
+
+    Simulator::Stop(Seconds(stop_time));
+    Simulator::Run();
+
+    if (flow_monitor)
+    {
+        flowHelper.SerializeToXmlFile(prefix_file_name + ".flowmonitor", true, true);
+    }
+
+    Simulator::Destroy();
+    return 0;
+}

timeserver/Makefile

@@ -0,0 +1,20 @@
+CC = gcc -Wall -std=c11 -pedantic
+SOURCES = timeserver.c 
+OBJECTS = timeserver.o 
+
+all: timeserver
+
+timeserver: $(OBJECTS)
+	$(CC) $(OBJECTS) -o timeserver
+
+timeserver.o: timeserver.c
+	$(CC) -c timeserver.c -o timeserver.o
+
+clean:
+	rm -f $(OBJECTS) timeserver timeserver.out
+
+clean_objects:
+	rm -f $(OBJECTS)
+
+run:
+	./timeserver

timeserver/README.md

@@ -0,0 +1,16 @@
+# Running the timeserver
+Use `make` to compile the timeserver.
+Use `make run` to run the timeserver. This will run on an infinite loop.
+Use `Ctrl+C` to stop the timeserver.
+
+## timeserver communication
+Communicating with the server can happen using netcat in UDP mode (-u flag).
+
+## timeserver information
+The timeserver runs on UDP port 8888.
+The timeserver will wait for `time\r\n` to be sent on this port, and if received,
+will send back a response of the time (in ms) since January 1st, 1970 (UNIX Epoch).
+
+## pcap information
+A demonstration of the timeserver has been captured with Wireshark in the 
+included `demo.pcap` file.

timeserver/timeserver.c

@@ -0,0 +1,83 @@
+// header files
+#include "timeserver.h"
+
+// constants
+// timeserver port is 8888
+#define TIMEPORT 8888
+#define BUFFER_SIZE 1024
+
+// prototypes
+
+// main function
+int main(int argc, char **argv)
+{
+    // initialize program (variables and structs)
+    bool quitFlag = true;
+    int socketTimeFD;
+    char message[BUFFER_SIZE];
+    struct sockaddr_in serverAddr, clientAddr;
+    memset(&serverAddr, 0, sizeof(serverAddr));
+    memset(&clientAddr, 0, sizeof(clientAddr));
+    // define a UDP socket
+    socketTimeFD = socket(AF_INET, SOCK_DGRAM, 0);
+    if(socketTimeFD < 0)
+    {
+        printf("Unable to create the socket.");
+        return -1;
+    }
+    // bind the UDP socket to port 8888 / TIMEPORT
+    serverAddr.sin_family = AF_INET;
+    serverAddr.sin_addr.s_addr = INADDR_ANY;
+    serverAddr.sin_port = htons(TIMEPORT);
+    int bindCheck = bind(socketTimeFD, &serverAddr, sizeof(serverAddr));
+    if(bindCheck < 0)
+    {
+        printf("Unable to bind the socket to the port or address.\n Is either in use?");
+        return -1;
+    }
+    // while loop to see if the "time\r\n" has been received (recv call?)
+    printf("Timeserver listening on port: %d\n", TIMEPORT);
+    while(quitFlag)
+    {
+        int clientAddrLen;
+        int receivedDataLen;
+        // grab the data from the client
+        receivedDataLen = recvfrom(socketTimeFD, message, BUFFER_SIZE, MSG_WAITALL, &clientAddr, &clientAddrLen);
+        message[receivedDataLen] = '\0';
+        // if "time\r\n" is received, then send() back the linux epoch.
+        if(strcmp(message, "time\n") == 0 || strcmp(message, "time\r\n") == 0)
+        {
+            // setup the reply message
+            char reply[BUFFER_SIZE];
+            // add the current time to the reply
+            sprintf(reply, "%d", time(NULL));
+            // send the reply to the requestee
+            sendto(socketTimeFD, (const char *)reply, strlen(reply), 0, (const struct sockaddr *) &clientAddr, clientAddrLen);
+            // log the time command recv'd
+            printf("\nServer received time. Replied with: %d\n", time(NULL));
+        }
+        else if (strcmp(message, "close\n") == 0 || strcmp(message, "quit\n") == 0 || strcmp(message, "q\n") == 0)
+        {
+            // if the server recv'd the close command, then close the server.
+            printf("\nServer received close.\n");
+            quitFlag = false;
+        }
+    }
+    // close the socket
+    close(socketTimeFD);
+    // profit???
+    return 0;
+}
+
+// function definitions
+
+/*
+Name: ???
+Process: ???
+Function Input/Parameters: ???
+Function Output/Parameters: ???
+Function Output/Returned: ???
+Device Input/Device: ???
+Device Output/Device: ???
+Dependencies: ???
+*/

timeserver/timeserver.h

@@ -0,0 +1,23 @@
+#ifndef TIMESERVER
+#define TIMESERVER
+
+// included libraries
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+#include <stdbool.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netdb.h>
+#include <time.h>
+#include <unistd.h>
+#include <errno.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+
+// data structures
+
+// function prototypes
+
+#endif // TIMESERVER