Socketpair 简介

socketpair - a slight generalization of pipes used for two-way stream communication.

以下内容来自：匠意雕码

今天用了一个从没玩过的socket函数socketpair()，它的作用是在进程内创建一对sock连接。乍一看好像也没什么，但是配合fork()使用之后就是各种欢乐。如下。

#define STRING1   "message from parent"
#define STRING2   "messgae from child"

#include <sys/types.h>

#include <sys/socket.h>
#include <stdio.h>
#include <errno.h>

main()
{
  int sockets[2], child;
  char buf[1024];

  /* Get the socket pair */
if (socketpair(AF_UNIX, SOCK_STREAM,
    0, sockets) < 0) {
 printf("error %d on socketpair\n", errno);
      exit(1);
  }

  /* create child process */
  if ((child = fork()) == -1) {
    printf("fork error %d\n", errno);
    exit(1);
  }

  if (child != 0) { /* this is the parent */
    /* close child's end of socket */
    close(sockets[0]);

    /* read message from child */
 if (read(sockets[1], buf, sizeof(buf)) < 0) {
 printf("error %d reading socket\n", errno);
      exit(1);
    }
    printf("-->%s\n", buf);

 /* write message to child */
 if (write(sockets[1], 
 STRING1, sizeof(STRING1)) < 0) {
 printf("error %d writing socket\n", errno);
      exit(1);
    } 

    /* finished */
    close(sockets[1]);

  } else {  /* the child */

    /* close parent's end of socket */
    close(sockets[1]);

    /* send message to parent */
    if (write(sockets[0], STRING2,
     sizeof(STRING1)) < 0) {

 printf("error %d writing socket\n", errno);
      exit(1);
    } 

    /* get message from parent */

 if (read(sockets[0], 
 buf, sizeof(buf)) < 0) {
printf("error %d reading socket\n", errno);
      exit(1);
    }
    printf("-->%s\n", buf);

    /* finished */
    close(sockets[0]);
  }
}