echoserv.cpp

/*

  ECHOSERV.C
  ==========
  (c) Paul Griffiths, 1999
  Email: mail@paulgriffiths.net
  
  Simple TCP/IP echo server.

    Modifications by Matthew Stoltenberg and James Hall:
        * apply SO_REUSEADDR
        * send and receive lines instead of just bytes

*/


#include <sys/socket.h>       /*  socket definitions        */
#include <sys/types.h>        /*  socket types              */
#include <arpa/inet.h>        /*  inet (3) funtions         */
#include <unistd.h>           /*  misc. UNIX functions      */

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>


/*  Global constants  */

#define ECHO_PORT          (2002)
#define MAX_LINE           (1000)


int main(int argc, char *argv[]) {
    int       list_s;                /*  listening socket          */
    int       conn_s;                /*  connection socket         */
    short int port;                  /*  port number               */
    struct    sockaddr_in servaddr;  /*  socket address structure  */
    char      buffer[MAX_LINE];      /*  character buffer          */
    char     *endptr;                /*  for strtol()              */
    int       reuse=1;               /*  for setsockopt            */


    /*  Get port number from the command line, and
        set to default port if no arguments were supplied  */

    if ( argc == 2 ) {
        port = strtol(argv[1], &endptr, 0);
        if ( *endptr ) {
            fprintf(stderr, "ECHOSERV: Invalid port number.\n");
            exit(EXIT_FAILURE);
        }
    }
    else if ( argc < 2 ) {
        port = ECHO_PORT;
    }
    else {
        fprintf(stderr, "ECHOSERV: Invalid arguments.\n");
        exit(EXIT_FAILURE);
    }


    /*  Create the listening socket  */

    if ( (list_s = socket(AF_INET, SOCK_STREAM, 0)) < 0 ) {
        fprintf(stderr, "ECHOSERV: Error creating listening socket.\n");
        exit(EXIT_FAILURE);
    }

    /* set SO_REUSEADDR so echoserv will be able to be re-run instantly on shutdown */
    if(setsockopt(list_s, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof(reuse)) == -1) {
        fprintf(stderr, "ECHOSERV: Error setting SO_REUSEADDR");
        close(list_s);
        exit(EXIT_FAILURE);
    }


    /*  Set all bytes in socket address structure to
        zero, and fill in the relevant data members   */

    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family      = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port        = htons(port);


    /*  Bind our socket addresss to the 
        listening socket, and call listen()  */

    if ( bind(list_s, (struct sockaddr *) &servaddr, sizeof(servaddr)) < 0 ) {
        fprintf(stderr, "ECHOSERV: Error calling bind()\n");
        exit(EXIT_FAILURE);
    }

    if ( listen(list_s, 2) < 0 ) {
        fprintf(stderr, "ECHOSERV: Error calling listen()\n");
        exit(EXIT_FAILURE);
    }

    
    /*  Enter an infinite loop to respond
        to client requests and echo input  */

    while ( 1 ) {
        int bytes;

        /*  Wait for a connection, then accept() it  */

        if ( (conn_s = accept(list_s, NULL, NULL) ) < 0 ) {
            fprintf(stderr, "ECHOSERV: Error calling accept()\n");
            exit(EXIT_FAILURE);
        }


        /*  Retrieve an input line from the connected socket
            then simply write it back to the same socket.     */

        bytes = recv(conn_s, buffer, MAX_LINE-1, 0);
        printf("Received: '%s'\n", buffer);
        send(conn_s, buffer, bytes, 0);


        /*  Close the connected socket  */

        if ( close(conn_s) < 0 ) {
            fprintf(stderr, "ECHOSERV: Error calling close()\n");
            exit(EXIT_FAILURE);
        }
    }
}