c++ socket实例

以下是一个简单的socket实例，它使用TCP协议在本地主机上创建一个服务器，并等待来自客户端的连接：

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

#define PORT 8080

int main(int argc, char const *argv[])
{
    int server_fd, new_socket;
    struct sockaddr_in address;
    int opt = 1;
    int addrlen = sizeof(address);
    char buffer[1024] = {0};
    const 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，允许重用地址和端口
    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到指定地址和端口
    if (bind(server_fd, (struct sockaddr *)&address, sizeof(address))<0)
    {
        perror("bind failed");
        exit(EXIT_FAILURE);
    }

    // 监听socket，等待客户端连接
    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);
    }

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

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

    // 关闭socket
    close(new_socket);
    close(server_fd);

    return 0;
}

运行该程序后，可以使用telnet工具连接到服务器并发送数据：

$ telnet localhost 8080
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
Hello from client
Hello from server
Connection closed by foreign host.

服务器将收到来自客户端的消息“Hello from client”，并发送回消息“Hello from server”。