Linux-进程间通信（四）: 域套接字

1. 域套接字：

(1) 只能用于同一设备上不同进程之间的通信；

(2) 效率高于网络套接字。域套接字仅仅是复制数据，并不走协议栈；

(3) 可靠，全双工；

2. 域套接字地址结构：

struct sockaddr_un {
    sa_family_t sun_family; /*AF_UNIX*/
    char sun_path[]; /*pathname*/
};

当我们将一个地址绑定至域套接字，系统用该路径名创建一个类型为S_IFSOCK的文件，尽告诉客户端名字，不能打开，也不能通信，

不会自动删除，需要程序完成后删除，若文件已存在则bind失败；

3. 测试代码：

server.c

 #include <sys/types.h>
 #include <sys/socket.h>
 #include <sys/un.h>
 #include <stdio.h>
 #include <stdlib.h>

 #define UN_PATH "/var/tmp/test_domain_socket"

 int main(int argc, char *argv[])
 {
     int sockfd = -;
     struct sockaddr_un un;
     int len = ;

     if ((sockfd = socket(AF_UNIX, SOCK_STREAM, )) < ){
         perror("create socket error\n");
         goto _ERROR;
     }

     memset(&un, , sizeof(un));
     un.sun_family = AF_UNIX;
     strcpy(un.sun_path, UN_PATH);

     len = sizeof(un.sun_family) + sizeof(un.sun_path);

     if (bind(sockfd, (struct sockaddr *)&un, len) < ){
         perror("socket bind error\n");
         goto _ERROR;
     }

     if (listen(sockfd, ) < ){
         perror("socket listen error\n");
     }

     int conn = accept(sockfd, (struct sockaddr *)&un, &len);
     if (conn < ){
         perror("accept error\n");
         goto _ERROR;
     }
     char buf[] = {};
     int n = read(conn, buf, );
     printf("recive-msg:%s", buf);
     write(conn, buf, n);
     close(conn);

     close(sockfd);
     unlink(UN_PATH);
     return ;

 _ERROR:
     if (sockfd != -){
         close(sockfd);
     }

     return -;
 }

client.c

 #include <sys/types.h>
 #include <sys/socket.h>
 #include <sys/un.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>

 #define UN_PATH "/var/tmp/test_domain_socket"

 int main(int argc, char *argv[])
 {
     int sockfd = -;
     struct sockaddr_un un;
     int len = ;

     if ((sockfd = socket(AF_UNIX, SOCK_STREAM, )) < ){
         perror("create socket error\n");
         goto _ERROR;
     }

     memset(&un, , sizeof(un));
     un.sun_family = AF_UNIX;
     strcpy(un.sun_path, UN_PATH);

     len = sizeof(un.sun_family) + sizeof(un.sun_path);

     if (connect(sockfd, (struct sockaddr *)&un, len) < ){
         perror("socket connect error\n");
         goto _ERROR;
     }

     char buf[] = {};
     int n = read(STDIN_FILENO, buf, );
     write(sockfd, buf, n);
     printf("send-msg:%s", buf);
     read(sockfd, buf, );
     buf[] = '\0';
     printf("recv-msg:%s", buf);

     close(sockfd);
     return ;

 _ERROR:
     if (sockfd != -){
         close(sockfd);
     }

     return -;
 }