编写一个socket的客户端和服务端

以下是一个简单的socket客户端和服务器端的代码示例：

### 服务器端

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

#define PORT 8080

int main() {
    int server_fd, new_socket, valread;
    struct sockaddr_in address;
    int opt = 1;
    int addrlen = sizeof(address);
    char buffer[1024] = {0};
    char *hello = "Hello from server";

    // 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 failed");
        exit(EXIT_FAILURE);
    }

    // 设置socket地址结构
    address.sin_family = AF_INET;
    address.sin_addr.s_addr = INADDR_ANY;
    address.sin_port = htons(PORT);

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

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

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

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

    printf("Client connected\n");

    // 从客户端读取数据
    valread = read(new_socket, buffer, 1024);
    printf("Received message: %s\n", buffer);

    // 向客户端发送数据
    send(new_socket, hello, strlen(hello), 0);
    printf("Hello message sent\n");

    return 0;
}

### 客户端

#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>

#define PORT 8080

int main(int argc, char const *argv[]) {
    int sock = 0, valread;
    struct sockaddr_in serv_addr;
    char *hello = "Hello from client";
    char buffer[1024] = {0};

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

    // 设置socket地址结构
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(PORT);

    // 将IP地址从点分十进制转换为网络字节序
    if (inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr) <= 0) {
        printf("\nInvalid address/ Address not supported \n");
        return -1;
    }

    // 连接服务器
    if (connect(sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0) {
        printf("\nConnection Failed \n");
        return -1;
    }

    printf("Connected to server\n");

    // 向服务器发送数据
    send(sock, hello, strlen(hello), 0);
    printf("Hello message sent\n");

    // 从服务器读取数据
    valread = read(sock, buffer, 1024);
    printf("Received message: %s\n", buffer);

    return 0;
}

该示例实现了一个简单的socket服务器和客户端。服务器端监听8080端口，当客户端连接成功后，从客户端读取数据并打印，然后向客户端发送一条“Hello from server”的消息。客户端连接到服务器，向服务器发送一条“Hello from client”的消息，然后从服务器读取数据并打印。