使用Linux Socket实现服务器和客户端对话

下面我将介绍如何使用Linux Socket编程实现一个简单的服务器和客户端对话系统。我们将使用C语言编写这个示例。

服务器端代码 (server.c)

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

#define PORT 8080
#define BUFFER_SIZE 1024

int main() {
    int server_fd, new_socket;
    struct sockaddr_in address;
    int opt = 1;
    int addrlen = sizeof(address);
    char buffer[BUFFER_SIZE] = {0};

    // 创建socket文件描述符
    if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0) {
        perror("socket failed");
        exit(EXIT_FAILURE);
    }

    // 设置socket选项
    if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT, &opt, sizeof(opt))) {
        perror("setsockopt");
        exit(EXIT_FAILURE);
    }

    address.sin_family = AF_INET;
    address.sin_addr.s_addr = INADDR_ANY;
    address.sin_port = htons(PORT);

    // 绑定socket到端口
    if (bind(server_fd, (struct sockaddr *)&address, sizeof(address)) < 0) {
        perror("bind failed");
        exit(EXIT_FAILURE);
    }

    // 监听连接
    if (listen(server_fd, 3) < 0) {
        perror("listen");
        exit(EXIT_FAILURE);
    }

    printf("Server listening on port %d...\n", PORT);

    // 接受连接
    if ((new_socket = accept(server_fd, (struct sockaddr *)&address, (socklen_t*)&addrlen)) < 0) {
        perror("accept");
        exit(EXIT_FAILURE);
    }

    printf("Client connected.\n");

    // 对话循环
    while(1) {
        // 读取客户端消息
        int valread = read(new_socket, buffer, BUFFER_SIZE);
        if (valread <= 0) {
            printf("Client disconnected or error occurred.\n");
            break;
        }

        printf("Client: %s\n", buffer);

        // 检查是否退出
        if (strcmp(buffer, "exit") == 0) {
            printf("Exit command received. Closing connection.\n");
            break;
        }

        // 清空缓冲区
        memset(buffer, 0, BUFFER_SIZE);

        // 获取服务器回复
        printf("Server: ");
        fgets(buffer, BUFFER_SIZE, stdin);
        buffer[strcspn(buffer, "\n")] = '\0'; // 移除换行符

        // 发送回复
        send(new_socket, buffer, strlen(buffer), 0);

        // 检查是否退出
        if (strcmp(buffer, "exit") == 0) {
            printf("Exit command sent. Closing connection.\n");
            break;
        }
    }

    // 关闭连接
    close(new_socket);
    close(server_fd);

    return 0;
}

客户端代码 (client.c)

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

#define PORT 8080
#define BUFFER_SIZE 1024

int main() {
    int sock = 0;
    struct sockaddr_in serv_addr;
    char buffer[BUFFER_SIZE] = {0};

    // 创建socket
    if ((sock = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
        printf("\n Socket creation error \n");
        return -1;
    }

    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(PORT);

    // 将IPv4地址从文本转换为二进制形式
    if (inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr) <= 0) {
        printf("\nInvalid address/ Address not supported \n");
        return -1;
    }

    // 连接到服务器
    if (connect(sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) {
        printf("\nConnection Failed \n");
        return -1;
    }

    printf("Connected to server. Type 'exit' to quit.\n");

    // 对话循环
    while(1) {
        // 获取用户输入
        printf("Client: ");
        fgets(buffer, BUFFER_SIZE, stdin);
        buffer[strcspn(buffer, "\n")] = '\0'; // 移除换行符

        // 发送消息到服务器
        send(sock, buffer, strlen(buffer), 0);

        // 检查是否退出
        if (strcmp(buffer, "exit") == 0) {
            printf("Exit command sent. Closing connection.\n");
            break;
        }

        // 清空缓冲区
        memset(buffer, 0, BUFFER_SIZE);

        // 读取服务器回复
        int valread = read(sock, buffer, BUFFER_SIZE);
        if (valread <= 0) {
            printf("Server disconnected or error occurred.\n");
            break;
        }

        printf("Server: %s\n", buffer);

        // 检查是否退出
        if (strcmp(buffer, "exit") == 0) {
            printf("Exit command received. Closing connection.\n");
            break;
        }
    }

    // 关闭socket
    close(sock);

    return 0;
}

编译和运行

1. 首先编译服务器和客户端程序：

gcc server.c -o server
gcc client.c -o client

2. 在一个终端窗口中运行服务器：

./server

3. 在另一个终端窗口中运行客户端：

./client

使用说明

1. 服务器启动后会监听8080端口，等待客户端连接
2. 客户端连接后，双方可以交替发送消息
3. 输入"exit"可以终止对话并关闭连接
4. 消息会显示在各自的终端上

扩展功能

如果需要扩展这个基础实现，可以考虑：

1. 支持多客户端连接（使用多线程或select/poll/epoll）
2. 添加消息加密功能
3. 实现文件传输功能
4. 添加用户认证机制
5. 实现更复杂的协议（如HTTP）

这个示例展示了最基本的Socket通信流程，实际应用中可能需要根据具体需求进行扩展和优化。