CS460-Projects/echoserver/echoserver.c

// 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)
    {
        // use the select() function here to check the set of sockets
        int selectedFD = select(maxFD+1, &socketList, 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, &socketList))
            {
                // 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: ???
*/