SERVER.C

/*
                                  Code Sample 25_2
*/

    /* server.c - code for example server program that uses TCP */

#ifndef unix
#define WIN32
#include <windows.h>
#include <winsock.h>
#else
#define closesocket close
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#endif

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

#define PROTOPORT       5193            /* default protocol port number */
#define QLEN            6               /* size of request queue        */

    int     visits      =   0;              /* counts client connections    */
    /*------------------------------------------------------------------------
     * Program:   server
     *
     * Purpose:   allocate a socket and then repeatedly execute the following:
     *              (1) wait for the next connection from a client
     *              (2) send a short message to the client
     *              (3) close the connection
     *              (4) go back to step (1)
     *
     * Syntax:    server [ port ]
     *
     *               port  - protocol port number to use
     *
     * Note:      The port argument is optional.  If no port is specified,
     *            the server uses the default given by PROTOPORT.
     *
     *------------------------------------------------------------------------
     */
    main(argc, argv)
    int     argc;
    char    *argv[];
    {
            struct  hostent  *ptrh;  /* pointer to a host table entry       */
            struct  protoent *ptrp;  /* pointer to a protocol table entry   */
            struct  sockaddr_in sad; /* structure to hold server's address  */
            struct  sockaddr_in cad; /* structure to hold client's address  */
            int     sd, sd2;         /* socket descriptors                  */
            int     port;            /* protocol port number                */
            int     alen;            /* length of address                   */
            char    buf[1000];       /* buffer for string the server sends  */

#ifdef WIN32
            WSADATA wsaData;
            WSAStartup(0x0101, &wsaData);
#endif
            memset((char *)&sad,0,sizeof(sad)); /* clear sockaddr structure */
            sad.sin_family = AF_INET;         /* set family to Internet     */
            sad.sin_addr.s_addr = INADDR_ANY; /* set the local IP address   */

            /* Check command-line argument for protocol port and extract    */
            /* port number if one is specified.  Otherwise, use the default */
            /* port value given by constant PROTOPORT                       */

            if (argc > 1) {                 /* if argument specified        */
                    port = atoi(argv[1]);   /* convert argument to binary   */
            } else {
                    port = PROTOPORT;       /* use default port number      */
            }
            if (port > 0)                   /* test for illegal value       */
                    sad.sin_port = htons((u_short)port);
            else {                          /* print error message and exit */
                    fprintf(stderr,"bad port number %s\n",argv[1]);
                    exit(1);
            }

            /* Map TCP transport protocol name to protocol number */

            if ( ((int)(ptrp = getprotobyname("tcp"))) == 0) {
                    fprintf(stderr, "cannot map \"tcp\" to protocol number");
                    exit(1);
            }

            /* Create a socket */

            sd = socket(PF_INET, SOCK_STREAM, ptrp->p_proto);
            if (sd < 0) {
                    fprintf(stderr, "socket creation failed\n");
                    exit(1);
            }

            /* Bind a local address to the socket */

            if (bind(sd, (struct sockaddr *)&sad, sizeof(sad)) < 0) {
                    fprintf(stderr,"bind failed\n");
                    exit(1);
            }

            /* Specify size of request queue */

            if (listen(sd, QLEN) < 0) {
                    fprintf(stderr,"listen failed\n");
                    exit(1);
            }

            /* Main server loop - accept and handle requests */

            while (1) {
                    alen = sizeof(cad);
                    if ( (sd2=accept(sd, (struct sockaddr *)&cad, &alen)) < 0) {
                            fprintf(stderr, "accept failed\n");
                            exit(1);
                    }
                    visits++;
                    sprintf(buf,"This server has been contacted %d time%s\n",
                            visits,visits==1?".":"s.");
                    send(sd2,buf,strlen(buf),0);
                    closesocket(sd2);
            }
    }