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[108]; /*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 = -1;
    struct sockaddr_un un;
    int len = 0;

    if ((sockfd = socket(AF_UNIX, SOCK_STREAM, 0)) < 0){
        perror("create socket error
");
        goto _ERROR;
    }

    memset(&un, 0, 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) < 0){
        perror("socket bind error
");
        goto _ERROR;
    }

    if (listen(sockfd, 5) < 0){
        perror("socket listen error
");
    }

    int conn = accept(sockfd, (struct sockaddr *)&un, &len);
    if (conn < 0){
        perror("accept error
");
        goto _ERROR;
    }
    char buf[64] = {0};
    int n = read(conn, buf, 63);
    printf("recive-msg:%s", buf);
    write(conn, buf, n);
    close(conn);

    close(sockfd);
    unlink(UN_PATH);
    return 0;

_ERROR:
    if (sockfd != -1){
        close(sockfd);
    }

    return -1;
}

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 = -1;
    struct sockaddr_un un;
    int len = 0;

    if ((sockfd = socket(AF_UNIX, SOCK_STREAM, 0)) < 0){
        perror("create socket error
");
        goto _ERROR;
    }

    memset(&un, 0, 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) < 0){
        perror("socket connect error
");
        goto _ERROR;
    }

    char buf[64] = {0};
    int n = read(STDIN_FILENO, buf, 63);
    write(sockfd, buf, n);
    printf("send-msg:%s", buf);
    read(sockfd, buf, 63);
    buf[64] = '';
    printf("recv-msg:%s", buf);

    close(sockfd);
    return 0;

_ERROR:
    if (sockfd != -1){
        close(sockfd);
    }

    return -1;
}