歡迎使用CSDN-markdown編輯器

LINUX 進程通信套接字，本地套接字與網絡套接字的區別

• 本地套接字的地址，一定要使用絕對路徑名，否則套接字將創建在當前目錄下，在非當前目錄運行客戶端程序，是無法找到此套接字文件的。也就無法通信成功。這是本地套接字的缺點。下面通過例程測試。

• 服務器端程序

/*  Make the necessary includes and set up the variables.  */

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

int main()
{
    int server_sockfd, client_sockfd;
    int server_len, client_len;
    struct sockaddr_un server_address;
    struct sockaddr_un client_address;

/*  Remove any old socket and create an unnamed socket for the server.  */

    unlink("server_socket");
    server_sockfd = socket(AF_UNIX, SOCK_STREAM, 0);

/*  Name the socket.  */

    server_address.sun_family = AF_UNIX;
    strcpy(server_address.sun_path, "server_socket");
    server_len = sizeof(server_address);
    bind(server_sockfd, (struct sockaddr *)&server_address, server_len);

/*  Create a connection queue and wait for clients.  */

    listen(server_sockfd, 5);
    while(1) {
        char ch;

        printf("server waiting\n");

/*  Accept a connection.  */

        client_len = sizeof(client_address);
        client_sockfd = accept(server_sockfd, 
            (struct sockaddr *)&client_address, &client_len);

/*  We can now read/write to client on client_sockfd.  */

        read(client_sockfd, &ch, 1);
        ch++;
        write(client_sockfd, &ch, 1);
        close(client_sockfd);
    }
}

• 客戶端程序

/*  Make the necessary includes and set up the variables.  */

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

int main()
{
    int sockfd;
    int len;
    struct sockaddr_un address;
    int result;
    char ch = 'A';

/*  Create a socket for the client.  */

    sockfd = socket(AF_UNIX, SOCK_STREAM, 0);

/*  Name the socket, as agreed with the server.  */

    address.sun_family = AF_UNIX;
    strcpy(address.sun_path, "server_socket");
    len = sizeof(address);

/*  Now connect our socket to the server's socket.  */

    result = connect(sockfd, (struct sockaddr *)&address, len);

    if(result == -1) {
        perror("oops: client1");
        exit(1);
    }

/*  We can now read/write via sockfd.  */

    write(sockfd, &ch, 1);
    read(sockfd, &ch, 1);
    printf("char from server = %c\n", ch);
    close(sockfd);
    exit(0);
}

生成的套接字文件在服務器程序所在目錄

客戶端在其他目錄，運行時候無法找到套接字，也就無法連接成功。

修改爲絕對路徑

#define  SOCKNAME "/tmp/mysock"

##服務器端修改套接字命名
strcpy(address.sun_path,SOCKNAME);

#客戶端修改
/*  Name the socket.  */

    server_address.sun_family = AF_UNIX;
    strcpy(server_address.sun_path,SOCKNAME  );

之前我沒意識到這個地址一定要是。。
對路徑。對應網絡編程，綁定的是端口號。不同的網絡服務協議，不同端口號。