Unix/Linux socket wypros

/* hello-world-server.c - a "hello world" server */



#include <stdio.h>              /* Basic I/O routines           */

#include <sys/types.h>          /* standard system types        */

#include <netinet/in.h>         /* Internet address structures  */

#include <sys/socket.h>         /* socket interface functions   */

#include <netdb.h>              /* host to IP resolution        */



#define PORT            6666        /* port of "hello world" server */

#define LINE    "hello world\n"   /* what to say to our clients  */



void main()

{

    int                 rc;       /* system calls return value storage  */

    int                 s;        /* socket descriptor                  */

    int                 cs;       /* new connection's socket descriptor */

    struct sockaddr_in  sa;       /* Internet address struct            */

    struct sockaddr_in  csa;      /* client's address struct            */

    int                 size_csa; /* size of client's address struct    */

    char msg[255];



    /* initiate machine's Internet address structure */

    /* first clear out the struct, to avoid garbage  */

    memset(&sa, 0, sizeof(sa));

    /* Using Internet address family */

    sa.sin_family = AF_INET;

    /* copy port number in network byte order */

    sa.sin_port = htons(PORT);

    /* we will accept cnnections coming through any IP  */

    /* address that belongs to our host, using the      */

    /* INADDR_ANY wild-card.                            */





    /* allocate a free socket                 */

    /* Internet address family, Stream socket */

    s = socket(AF_INET, SOCK_STREAM, 0);

    if (s < 0) {

        perror("socket: allocation failed");

    }



    /* bind the socket to the newly formed address */

    rc = bind(s, (struct sockaddr *)&sa, sizeof(sa));



    /* check there was no error */

    if (rc) {

        perror("bind");

        exit(1);

    }



    /* ask the system to listen for incoming connections        */

    /* to the address we just bound. specify that up to         */

    /* 5 pending connection requests will be queued by the      */

    /* system, if we are not directly awaiting them using       */

    /* the accept() system cal, when they arrive.               */

    rc = listen(s, 5);



    /* check there was no error */

    if (rc) {

        perror("listen");

    }



    /* remember size for later usage */

    size_csa = sizeof(csa);



    /* enter an accept-write-close infinite loop */

    while (1) {

        /* the accept() system call will wait for a     */

        /* connection, and when one is established, a   */

        /* new socket will be created to form it, and   */

        /* the csa variable will hold the address       */

        /* of the Client that just connected to us.     */

        /* the old socket, s, will still be available   */

        /* for future accept() statements.              */

        cs = accept(s, (struct sockaddr *)&csa, &size_csa);



        /* check for errors. if any, enter accept mode again */

        if (cs < 0)

            continue;



        /* ok, we got a new connection. do the job... */

        write(cs, LINE, sizeof(LINE));



        /* now close the connection */

        close(cs);

    }

}