用c语言写一段socket程序，实现服务器和客户端TCP/IP通信，编写客户端向服务器发送"HELLO",服务器端ip地址为192.168.0.7，端口号是6000

在C语言中，我们可以使用标准库`sys/socket.h`和`netinet/in.h`来编写简单的TCP/IP服务器和客户端程序。下面是一个简化的示例，演示了如何创建一个服务器监听来自客户端的连接，并处理"HELLO"消息。

**服务器端代码（server.c）**:

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

#define PORT 6000
#define MAX_CLIENTS 5

int main() {
    int server_socket, client_socket;
    struct sockaddr_in server_addr, client_addr;
    char buffer[100];

    // 创建服务器套接字
    server_socket = socket(AF_INET, SOCK_STREAM, 0);
    if (server_socket == -1) {
        perror("Failed to create server socket");
        exit(1);
    }

    // 设置服务器地址
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(PORT);
    inet_pton(AF_INET, "192.168.0.7", &server_addr.sin_addr);

    // 绑定并监听
    if (bind(server_socket, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1) {
        perror("Failed to bind server");
        close(server_socket);
        exit(1);
    }
    listen(server_socket, MAX_CLIENTS);

    printf("Server listening on %s:%d...\n", inet_ntoa(server_addr.sin_addr), ntohs(server_addr.sin_port));

    while (1) {
        // 接受客户端连接
        client_socket = accept(server_socket, (struct sockaddr*)&client_addr, NULL);
        if (client_socket == -1) {
            perror("Accept failed");
            continue;
        }

        // 读取数据
        read(client_socket, buffer, sizeof(buffer));
        buffer[strcspn(buffer, "\r\n")] = '\0'; // 移除换行符
        printf("Received message: %s\n", buffer);

        // 发送响应
        write(client_socket, "HELLO from server!\n", strlen("HELLO from server!"));

        // 关闭连接
        close(client_socket);
    }

    return 0;
}

**客户端代码（client.c）**:

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

#define SERVER_IP "192.168.0.7"
#define PORT 6000

int main() {
    int client_socket;
    struct sockaddr_in server_addr;
    char message[] = "HELLO";

    // 创建客户端套接字
    client_socket = socket(AF_INET, SOCK_STREAM, 0);
    if (client_socket == -1) {
        perror("Failed to create client socket");
        exit(1);
    }

    // 设置服务器地址
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(PORT);
    inet_aton(SERVER_IP, &server_addr.sin_addr);

    // 连接到服务器
    if (connect(client_socket, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1) {
        perror("Connect failed");
        close(client_socket);
        exit(1);
    }

    // 发送消息
    send(client_socket, message, strlen(message), 0);
    printf("Sent message: '%s'\n", message);

    // 读取服务器响应
    char response[100];
    recv(client_socket, response, sizeof(response), 0);
    printf("Received response: %s\n", response);

    // 关闭连接
    close(client_socket);

    return 0;
}

要运行这个程序，首先编译服务器端代码然后启动服务器（`./server`），接着编译客户端代码并运行（`./client`）。客户端将连接到指定的IP和端口并向服务器发送"HELLO"，服务器会回应"HELLO from server!"。