Linux socket连接句柄进程间传送示例代码
准备做一个网络侦听进程和数据处理进程分离的模块，侦听进程和数据处理进程一对多关系，希望侦听进程在收到连接后，把socket句柄传送给空闲的数据处理进程。对于进程间文件描述符传送，先做了如下的示例程序。
#include <stdio.h>#include <stdlib.h>#include <stdint.h>#include <errno.h>#include <sys/types.h>#include <sys/socket.h>#include <sys/select.h>#include <sys/un.h>#include <netinet/in.h>#include <sys/wait.h>#include <sys/uio.h>/** * Author: luckysym * Date: 3/22/2013 * *Global Variables: *int client_pipe_fd 与子进程通讯的fd，用于向子进程发送远程socket句柄 * * Functions: * create_inet_server() 创建tcp侦听服务，父进程调用 * create_pipe_server() 创建本地管道侦听服务，父进程调用 * pipe_connect() 子进程连接父进程的管道 * inet_client_connected() 父进程收到远程tcp连接的处理函数，收到连接后将句柄发送到子进程 * pipe_client_connected() 父进程收到子进程的管道连接处理函数，函数中将管道句柄保存为全局变量 * wait_for_connect() 父进程等待socket连接，包括等待子进程管道连接，或者远程tcp连接， * 收到连接后根据socket类型分别调用inet_client_connected() * 或pipe_client_connected() * recv_fd() 子进程用于接收父进程发来的远程socket句柄 * *child_main() 子进程主函数 * * 程序测试执行过程： * 1. 父进程main函数启动后立即fork一个子进程，然后创建管道监听 * 2. 子进程启动后，等待5秒钟后（保证父进程管道创建完毕），连接父进程管道 * 3. 父进程收到子进程的管道连接后，保存管道通讯句柄，然后创建tcp侦听（端口30098） * 4. 子进程连接父进程完毕后，等待接收父进程的管道消息 * * 4. 远程启动一个telnet连接到30098端口。 * 5. 父进程收到连接后，首先向远程发送"Hello Client"消息 * 6. 然后父进程将tcp连接句柄通过管道发送给子进程（发送过程中句柄被复制） * 7. 发送完毕后，父进程关闭tcp连接句柄 * 8. 子进程收到tcp连接句柄后，向远程telnet发送"This is child process speaking"消息 * 然后准备读取该tcp连接句柄。 * 9. 远程telnet端输入并发送一条文本消息，子进程在收到消息后会将其打印出（以[child]为前缀） * 10. 子进程打印出消息后，关闭tcp连接句柄，telnet端连接同时关闭。 */int client_pipe_fd = 0;int create_inet_server(uint16_t port){int fd = socket(PF_INET, SOCK_STREAM | SOCK_NONBLOCK, 0);if ( fd < 0 ) {printf("failed to create socket, err=%d\n", errno);return fd;}struct sockaddr_in laddr;laddr.sin_family = AF_INET;laddr.sin_port = htons(port);laddr.sin_addr.s_addr = htonl(INADDR_ANY);int ret = bind(fd, (struct sockaddr*)&laddr, sizeof(laddr));if ( ret < 0 ) {printf("failed to bind local port %d, err=%d\n", port, errno);return ret;}ret = listen(fd, 10);if ( ret < 0 ) {printf("failed to listen, err=%d", errno);return ret;}return fd;}int create_pipe_server(const char * path){int fd = socket(PF_UNIX, SOCK_STREAM , 0);if ( fd < 0 ) {printf("failed to create pipe, err=%d\n", errno);return fd;}struct sockaddr_un laddr;memset(&laddr, 0, sizeof(laddr));laddr.sun_family = AF_LOCAL;strcpy(laddr.sun_path, path);//laddr.sun_len = sizeof(laddr.sun_length) + sizeof(laddr.sun_family) + strlen(laddr.sun_path) + 1;int ret = bind(fd, (struct sockaddr*)&laddr, sizeof(laddr));if ( ret < 0 ) {printf("failed to bind local path %s, err=%d\n", path, errno);return ret;}ret = listen(fd, 10);if ( ret < 0 ) {printf("failed to listen pipe, err=%d", errno);return ret;}return fd;}int pipe_connect(const char * local, const char * remote){struct sockaddr_un laddr;struct sockaddr_un raddr;laddr.sun_family = AF_LOCAL;raddr.sun_family = AF_LOCAL;strcpy(laddr.sun_path, local);strcpy(raddr.sun_path, remote);int llen = strlen(laddr.sun_path) + sizeof(laddr.sun_family) + 1;int rlen = strlen(raddr.sun_path) + sizeof(raddr.sun_family) + 1;unlink(local);int fd = socket(PF_UNIX, SOCK_STREAM, 0);if (fd < 0) {printf("create client pipe socket fail, err=%d\n", errno);return fd;}int ret = bind(fd, (struct sockaddr *)&laddr, llen);if ( ret < 0) {printf("bind local pipe path fail - %s, %d\n", local, errno);return ret;}ret = connect(fd, (struct sockaddr *)&raddr, rlen );if (ret < 0 ) {printf("connect to remote pipe fail, errno=%d\n", errno);return ret;}return fd;}int inet_client_connected(int sock, const struct sockaddr * raddr, socklen_t size){printf("Connection comming\n");int ret = write(sock, "Hello Client!\n", 15);struct cmsghdr * cmptr = 0;struct msghdr msg;struct iovec iov[1];char buf[2];iov[0].iov_base = buf;iov[0].iov_len = 2;msg.msg_iov = iov;msg.msg_iovlen = 1;msg.msg_name = NULL;msg.msg_namelen = 0;cmptr = (struct cmsghdr *)malloc(sizeof(struct cmsghdr) + sizeof(int));cmptr->cmsg_level = SOL_SOCKET;cmptr->cmsg_type = SCM_RIGHTS;cmptr->cmsg_len = sizeof(struct cmsghdr) + sizeof(int);*(int *)CMSG_DATA(cmptr) = sock;msg.msg_control = cmptr;msg.msg_controllen = sizeof(struct cmsghdr) + sizeof(int);buf[1] = 0; buf[0] = 1;ret = sendmsg(client_pipe_fd, &msg, 0);if ( ret != 2) {printf("send socket fd failed, ret=%d, err=%d\n", ret, errno);}free(cmptr);close(sock);return 0;}int pipe_client_connected(int sock, const struct sockaddr * addr, socklen_t size){const struct sockaddr_un * paddr = (const struct sockaddr_un *)addr;printf("client pipe connected fd=%d\n", sock);client_pipe_fd = sock;return -1;}#define INET_SOCK 0#define PIPE_SOCK 1int wait_for_connect(int sock, int type){fd_set rds;int ret = 0;struct timeval times;struct sockaddr_in riaddr;struct sockaddr_un ruaddr;socklen_t rsize[] = { sizeof(riaddr), sizeof(ruaddr) };struct sockaddr * paddrs[] = { (struct sockaddr*)&riaddr, (struct sockaddr*)&ruaddr};while ( !ret ) {times.tv_sec = 1;times.tv_usec = 0;FD_ZERO(&rds);FD_SET(sock, &rds);ret = select(sock + 1, &rds, 0, 0, ×);if ( ret < 0 ) {printf("select fail. err=%d\n", errno);break;} else if ( ret == 0) {continue;} else {ret = accept(sock, paddrs[type], &rsize[type]);if ( ret < 0 ) {break;} else {if ( type == INET_SOCK) {ret = inet_client_connected(ret, paddrs[INET_SOCK], rsize[INET_SOCK]);} else if ( type == PIPE_SOCK ) {ret = pipe_client_connected(ret, paddrs[PIPE_SOCK], rsize[PIPE_SOCK]);}if ( ret < 0 ) break;}}ret = 0;} // whilereturn 0;}int recv_fd(int pipefd){char buf[2];int newfd = -1;struct iovec iov[1];struct msghdr msg;struct cmsghdr * cmptr = (struct cmsghdr *)malloc(sizeof(struct cmsghdr) + sizeof(int));iov[0].iov_base = buf;iov[0].iov_len = sizeof(buf);msg.msg_iov = iov;msg.msg_iovlen = 1;msg.msg_name = NULL;msg.msg_namelen = 0;msg.msg_control = cmptr;msg.msg_controllen = sizeof(struct cmsghdr) + sizeof(int);int ret = recvmsg(pipefd, &msg, 0);printf("[child] recvmsg returned, ret=%d\n", ret);if ( ret < 0 ) {printf("recvmsg failed, err=%d\n", errno);} else {newfd = *(int*)CMSG_DATA(cmptr);printf("[child] recv the socket fd: %d\n", newfd);}free(cmptr);return newfd;}int child_main(){printf("[child] child process running, wait 5 secs for pipe server creation\n");sleep(5);int fd = pipe_connect("/tmp/pipe_local", "/tmp/fd_trans");printf("[child] connect to remote pipe fd = %d\n", fd);int newfd = recv_fd(fd);int ret = write(newfd, "[child] This is child process speaking!\n", 41);if ( ret < 0 ) {printf("[child] write message to remote fail: ret=%d, err=%d\n", ret, errno);}char buf[256];memset(buf, 0, sizeof(buf));ret = read(newfd, buf, 256);if ( ret < 0) {printf("[child] failed to recv remote message: \n");} else {buf[ret] = 0;printf("[child] remote message arrived: %s\n", buf);}printf("[child] child exiting\n");close(fd);close(newfd);return 0;}int main(int argc, char *argv){if ( fork() == 0 ) {exit(child_main());}unlink("/tmp/fd_trans");int pipesock = create_pipe_server("/tmp/fd_trans");if (pipesock >= 0) {printf("pipe server created, now wait for child connecting\n");wait_for_connect(pipesock, PIPE_SOCK);}int inetsock = create_inet_server(30098);if ( inetsock >= 0 ) wait_for_connect(inetsock, INET_SOCK);close(client_pipe_fd);close(pipesock);close(inetsock);return 0;}