linux socket 判断连接是否断开 send和recv函数

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文章目录

前言
[一、如何判断连接是否断开 send和recv函数？](#一、如何判断连接是否断开 send和recv函数？)
二、代码示例
总结

前言

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介绍linux socket 判断连接是否断开 send和recv函数

提供示例代码： ser端 3秒发送一个命令给 cli端，然后cli端处理命令

提示：以下是本篇文章正文内容，下面案例可供参考

一、如何判断连接是否断开 send和recv函数？

send:

send() 或 sendto() 函数发送数据时，当尝试向一个已经关闭的套接字发送数据时，默认情况下会生成 SIGPIPE 信号给你的进程，导致进程退出

可以使用 MSG_NOSIGNAL 标志来避免生成 SIGPIPE 信号。

c 复制代码

 ssize_t send_received = send(clifd, cmd_buf, sizeof(cmd_buf) - 1, MSG_NOSIGNAL);
        printf("send_received = %d\n", send_received);
        if (send_received == -1) {
            if (errno == EPIPE) {
                    printf("Client disconnected.\n");
                } else {
                    perror("Send failed");
                }
            close(clifd);
            return -1;
        }

recv:

可以判断返回值 recv返回 0表述对端关闭

c 复制代码

ssize_t bytes_received = recv(sockfd, cmd_buf, sizeof(cmd_buf) - 1, 0);
        if (bytes_received < 0) {
            perror("recv failed");
            close(sockfd);
            return -1;
        } else if (bytes_received == 0) {
            printf("ser closed\n");
            close(sockfd);
            return 0;
        }

二、代码示例

socket_cmd.h

c 复制代码

#ifndef __SOCKET_CMD_H__
#define __SOCKET_CMD_H__



typedef enum {
    CMD_TYPE_TEST = 0x1100,
    CMD_TYPE_EXEC,
    CMD_TYPE_DOWNLOAD,
    CMD_TYPE_UPLOAD,


    CMD_TYPE_MAX,
} cmd_type_t;

typedef enum {
    OP_TYPE_TEST = 0x2100,
    OP_TYPE_REQ,
    OP_TYPE_ACK,
    OP_TYPE_FAIL,


    OP_TYPE_MAX,
} op_type_t;


struct s_cmd
{
    int cmd;
    int op;
    char msg[256];
};

#endif

socket_cmd_ser.c

c 复制代码

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <errno.h>

#include "socket_cmd.h"

#define SERVER_IP "127.0.0.1" // 服务器的 IP 地址
#define SERVER_PORT 8080       // 服务器的端口号

int ser_sock_create(char * addr, int port, int listen_num)
{
    char s_ip[16] = {0};
    int sockfd;
    int clifd;
    struct sockaddr_in server_addr = {0}; 
    struct sockaddr_in client_addr = {0};
    char cmd_buf[512] = {0};
    int ret = 0;
    int addr_len = 0;

    if(addr == NULL || port > 65535 || port < 0 || listen_num <= 0 || listen_num > 1024)
    {
        return -1;
    }

    printf("addr = %s, port = %d, listen_num = %d\n", addr, port, listen_num);

    memcpy(s_ip, addr, strnlen(addr, 16));
    // 创建套接字
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) {
        perror("socket creation failed");
        return -1;
    }

        // Set the SO_REUSEADDR option
    int optval = 1;
    if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval)) == -1) {
        perror("Setsockopt failed");
        close(sockfd);
        return 1;
    }

    // 设置客户端地址信息
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(port); // 客户端绑定的端口号
    server_addr.sin_addr.s_addr = inet_addr(s_ip); // 绑定所有可用接口

    // 绑定套接字到客户端地址
    if (bind(sockfd, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) {
        perror("bind failed");
        close(sockfd);
        return -1;
    }

    addr_len = sizeof(client_addr);
    // 获取并打印绑定的 IP 地址和端口号
    if (getsockname(sockfd, (struct sockaddr *)&server_addr, &addr_len) == -1) {
        perror("getsockname failed");
        close(sockfd);
        return -1;
    }
    
    char ip_str[INET_ADDRSTRLEN];
    inet_ntop(AF_INET, &server_addr.sin_addr, ip_str, sizeof(ip_str));
    
    printf("ser bind %s:%d\n", ip_str, ntohs(server_addr.sin_port));

    // 开始监听连接
    if (listen(sockfd, listen_num) < 0) {
        perror("Listen failed");
        return -1;
    }

    clifd = accept(sockfd, NULL, NULL);
    if (clifd < 0) {
        perror("Accept failed");
        return -1;
    }

    // 这里可以添加发送和接收数据的代码
    while(1)
    {
        memset(cmd_buf, 0, sizeof(cmd_buf));
        struct s_cmd cmd = {0};
        cmd.cmd = CMD_TYPE_TEST;
        cmd.op = OP_TYPE_TEST;
        memcpy(cmd.msg, "hello cmd", strnlen( "hello cmd", 128));
        memcpy(cmd_buf, &cmd, sizeof(cmd));
        ssize_t send_received = send(clifd, cmd_buf, sizeof(cmd) , MSG_NOSIGNAL);
        //ssize_t send_received = write(clifd, cmd_buf, sizeof(cmd_buf) - 1);
        printf("send_received = %d\n", send_received);
        if (send_received == -1) {
            if (errno == EPIPE) {
                    printf("Client disconnected.\n");
                } else {
                    perror("Send failed");
                }
            close(clifd);
            return -1;
        }

        usleep(3* 1000 * 1000);
    }


    // 关闭套接字
    close(sockfd);
}


int main() {
    int sockfd;

    ser_sock_create("0.0.0.0", 9090, 1);

    return 0;
}

socket_cmd_cli.c

c 复制代码

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include "socket_cmd.h"

#define SERVER_IP "127.0.0.1" // 服务器的 IP 地址
#define SERVER_PORT 8080       // 服务器的端口号
#define CLIENT_PORT 19091       // 客户端绑定的端口号


int cli_cmd_dispatch(struct s_cmd * cmd)
{
    struct s_cmd* tmp_cmd = NULL;

    if(cmd == NULL)
    {
        return -1;
    }

    tmp_cmd = malloc(sizeof(struct s_cmd));
    if(tmp_cmd == NULL)
    {
        return -1;
    }

    memcpy(tmp_cmd, cmd, sizeof(struct s_cmd));
    
    switch(tmp_cmd->cmd)
    {
        case CMD_TYPE_TEST:
        
            break;
        
        
        default:
            break;
    
    }

    free(tmp_cmd);
    return 0;
}


int cli_check_cmd_valid(struct s_cmd * cmd)
{
    if(cmd == NULL)
    {
        return -1;
    }
    
    
    
    return 0;
}

int cli_sock_create(char * seraddr, int serport, char * cliaddr, int cliport)
{
    char s_ip[16] = {0};
    char c_ip[16] = {0};
    int sockfd;
    struct sockaddr_in server_addr = {0}; 
    struct sockaddr_in client_addr = {0};
    char cmd_buf[512] = {0};
    int ret = 0;
    int addr_len = 0;

    if(seraddr == NULL || serport > 65535 || serport < 0 || cliport < 0 || cliport > 65535)
    {
        return -1;
    }

    if(cliaddr == NULL)
    {
        memcpy(c_ip, "0.0.0.0", strnlen("0.0.0.0", 16));
    }else
    {
        memcpy(c_ip, cliaddr, strnlen(cliaddr, 16));
    }

    memcpy(s_ip, seraddr, strnlen(seraddr, 16));
    // 创建套接字
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) {
        perror("socket creation failed");
        exit(EXIT_FAILURE);
    }

    // 设置客户端地址信息
    client_addr.sin_family = AF_INET;
    client_addr.sin_port = htons(CLIENT_PORT); // 客户端绑定的端口号
    client_addr.sin_addr.s_addr = inet_addr(c_ip); // 绑定所有可用接口

    // 绑定套接字到客户端地址
    if (bind(sockfd, (struct sockaddr *)&client_addr, sizeof(client_addr)) < 0) {
        perror("bind failed");
        close(sockfd);
        exit(EXIT_FAILURE);
    }

    addr_len = sizeof(client_addr);
    // 获取并打印绑定的 IP 地址和端口号
    if (getsockname(sockfd, (struct sockaddr *)&client_addr, &addr_len) == -1) {
        perror("getsockname failed");
        close(sockfd);
        exit(EXIT_FAILURE);
    }
    
    char ip_str[INET_ADDRSTRLEN];
    inet_ntop(AF_INET, &client_addr.sin_addr, ip_str, sizeof(ip_str));
    
    printf("cli bind %s:%d\n", ip_str, ntohs(client_addr.sin_port));

    // 设置服务器地址信息
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(serport);
    server_addr.sin_addr.s_addr = inet_addr(s_ip);

    // 连接到服务器
    if (connect(sockfd, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) {
        perror("connection to server failed");
        close(sockfd);
        exit(EXIT_FAILURE);
    }

    printf("connetct to ser %s:%d\n", s_ip, serport);

    // 这里可以添加发送和接收数据的代码
    while(1)
    {
        struct s_cmd cmd = {0};
        memset(cmd_buf, 0, sizeof(cmd_buf));
        ssize_t bytes_received = recv(sockfd, cmd_buf, sizeof(struct s_cmd), 0);
        if (bytes_received < 0) {
            perror("recv failed");
            close(sockfd);
            return -1;
        } else if (bytes_received == 0) {
            printf("ser closed\n");
            close(sockfd);
            return 0;
        }
        memcpy(&cmd, cmd_buf, sizeof(struct s_cmd));
        printf("bytes_received = %d, cmd.cmd = 0x%x, cmd.op = 0x%x, cmd.msg = %s\n", bytes_received, cmd.cmd, cmd.op, cmd.msg);
        
        if(cli_check_cmd_valid(&cmd) == 0)
        {
            cli_cmd_dispatch(&cmd);
        }
    }


    // 关闭套接字
    close(sockfd);
}


int main() {
    int sockfd;

    cli_sock_create("127.0.0.1", 9090, NULL, 0);

    return 0;
}

总结

socket通信 ser端 3秒发送一个命令给 cli端，然后cli端处理命令的代码和如何判断socket对端断开连接。