01lst02.c

目前已经有很多介绍计算机网络的书籍

/* Listing 1.2 :
 *
 * Example performing I/O on a Socket Pair :
 */
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>

int
main(int argc,char **argv) {
    int z;              /* Status return code */
    int s[2];           /* Pair of sockets */
    char *cp;           /* A work pointer */
    char buf[80];       /* Work buffer */

    /*
     * Create a pair of local sockets :
     */
    z = socketpair(AF_LOCAL,SOCK_STREAM,0,s);

    if ( z == -1 ) {
        fprintf(stderr,
            "%s: socketpair(AF_LOCAL,SOCK_STREAM,"
            "0)\n",
            strerror(errno));
        return 1;           /* Failed */
    }

    /*
     * Write a message to socket s[1] :
     */
    z = write(s[1],cp="Hello?",6);
    if ( z < 0 ) {
        fprintf(stderr,
            "%s: write(%d,\"%s\",%d)\n",
            strerror(errno),s[1],cp,strlen(cp));
        return 2;   /* Failed write */
    }

    printf("Wrote message '%s' on s[1]\n",cp);

    /*
     * Read from socket s[0] :
     */
    z = read(s[0],buf,sizeof buf);
    if ( z < 0 ) {
        fprintf(stderr,
            "%s: read(%d,buf,%d)\n",
            strerror(errno),s[0],sizeof buf);
        return 3;   /* Failed read */
    }

    /*
     * Report received message :
     */
    buf[z] = 0;    /* NUL terminate */
    printf("Received message '%s' from socket s[0]\n",
        buf);

    /*
     * Send a reply back to s[1] from s[0] :
     */
    z = write(s[0],cp="Go away!",8);
    if ( z < 0 ) {
        fprintf(stderr,
            "%s: write(%d,\"%s\",%d)\n",
            strerror(errno),s[0],cp,strlen(cp));
        return 4;   /* Failed write */
    }

    printf("Wrote message '%s' on s[0]\n",cp);

    /*
     * Read from socket s[1] :
     */
    z = read(s[1],buf,sizeof buf);
    if ( z < 0 ) {
        fprintf(stderr,
            "%s: read(%d,buf,%d)\n",
            strerror(errno),s[1],sizeof buf);
        return 3;   /* Failed read */
    }

    /*
     * Report message received by s[0] :
     */
    buf[z] = 0;    /* NUL terminate */
    printf("Received message '%s' from socket s[1]\n",
        buf);

    /*
     * Close the sockets :
     */
    close(s[0]);
    close(s[1]);

    puts("Done.");
    return 0;
}