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今天在阅读 nginx 源码时发现 socketpair 这个函数，开始还以为是 nginx 中自定义的函数，man 一下后才发现，还有父子进程间通讯的作用，以下是该函数的说明：
SOCKETPAIR(2) Linux Programmer’s Manual SOCKETPAIR(2)
NAME
socketpair - create a pair of connected sockets
SYNOPSIS
#include <sys/types.h> /* See NOTES */
#include <sys/socket.h>
int socketpair(int domain, int type, int protocol, int sv[2]);
DESCRIPTION
The socketpair() call creates an unnamed pair of connected sockets in the specified domain, of the specified
type, and using the optionally specified protocol. For further details of these arguments, see socket(2).
The descriptors used in referencing the new sockets are returned in sv[0] and sv[1]. The two sockets are
indistinguishable.
RETURN VALUE
On success, zero is returned. On error, -1 is returned, and errno is set appropriately.
以下是一个父子进程通讯的例子：
#include <stdio.h>
#include <stdlib.h>
#include <unistd.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 */
struct msghdr msg;
struct iovec iov[1];
char send_buf[100] = "TEST";
struct msghdr msgr;
struct iovec iovr[1];
char recv_buf[100];
/*
* 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 */
}
/*
* Sendmsg s[1]:
*/
bzero(&msg, sizeof(msg));
msg.msg_name = NULL; /* attention this is a pointer to void* type */
msg.msg_namelen = 0;
iov[0].iov_base = send_buf;
iov[0].iov_len = sizeof(send_buf);
msg.msg_iov = iov;
msg.msg_iovlen = 1;
printf("sendmsg begin./n");
z = sendmsg( s[1], &msg, 0 );
if(z == -1 )
{ fprintf(stderr,"Sendmsg failed. errno : %s/n",strerror(errno));
return -1;
}
printf("Sendmsg Success!/n");
/*
* Read from socket s[0]:
*/
bzero(&msg, sizeof(msg));
msgr.msg_name = NULL; /* attention this is a pointer to void* type */
msgr.msg_namelen = 0;
iovr[0].iov_base = &recv_buf;
iovr[0].iov_len = sizeof(recv_buf);
msgr.msg_iov = iovr;
msgr.msg_iovlen = 1;
z = recvmsg( s[0], &msgr, 0);
if(z == -1 )
{ fprintf(stderr,"Recvmsg failed. errno : %s/n",strerror(errno));
return -1;
}
printf("Recvmsg Success!/n");
printf("recvmsg : %s/n", recv_buf);
/*
* Close the sockets:
*/
close(s[0]);
close(s[1]);
puts("Done");
return 0;
}
Very good