CentOS环境下C++如何进行网络编程 - 问答

在CentOS环境下进行C++网络编程，通常会使用套接字（socket）API。以下是一个简单的步骤指南，包括如何安装必要的库、编写一个基本的TCP服务器和客户端程序。

步骤 1: 安装开发工具和库

首先，确保你的CentOS系统已经安装了必要的开发工具和库。你可以使用以下命令来安装它们：

sudo yum groupinstall "Development Tools"
sudo yum install zlib-devel bzip2-devel openssl-devel ncurses-devel sqlite-devel readline-devel tk-devel gdbm-devel db4-devel libpcap-devel xz-devel

步骤 2: 编写TCP服务器

创建一个名为tcp_server.cpp的文件，并添加以下代码来创建一个简单的TCP服务器：

#include <iostream>
#include <cstring>
#include <sys/socket.h>
#include <netinet/in.h>
#include <unistd.h>

int main() {
    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";

    // Creating socket file descriptor
    if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0) {
        perror("socket failed");
        exit(EXIT_FAILURE);
    }

    // Forcefully attaching socket to the port 8080
    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(8080);

    // Forcefully attaching socket to the port 8080
    if (bind(server_fd, (struct sockaddr*)&address, sizeof(address)) < 0) {
        perror("bind failed");
        exit(EXIT_FAILURE);
    }

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

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

    read(new_socket, buffer, 1024);
    std::cout << buffer << std::endl;
    send(new_socket, hello, strlen(hello), 0);
    std::cout << "Hello message sent\n";

    close(new_socket);
    close(server_fd);

    return 0;
}

步骤 3: 编写TCP客户端

创建一个名为tcp_client.cpp的文件，并添加以下代码来创建一个简单的TCP客户端：

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

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

    if ((sock = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
        std::cout << "\n Socket creation error \n";
        return -1;
    }

    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(8080);

    // Convert IPv4 and IPv6 addresses from text to binary form
    if(inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr) <= 0) {
        std::cout << "\nInvalid address/ Address not supported \n";
        return -1;
    }

    if (connect(sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) < 0) {
        std::cout << "\nConnection Failed \n";
        return -1;
    }

    send(sock, hello, strlen(hello), 0);
    std::cout << "Hello message sent\n";
    read(sock, buffer, 1024);
    std::cout << "Server: " << buffer << std::endl;

    close(sock);

    return 0;
}

步骤 4: 编译程序

使用g++编译器编译服务器和客户端程序：

g++ -o tcp_server tcp_server.cpp
g++ -o tcp_client tcp_client.cpp

步骤 5: 运行程序

首先运行服务器：

./tcp_server

然后在另一个终端运行客户端：

./tcp_client

你应该会看到服务器接收到了客户端发送的消息，并且客户端接收到了服务器的回复。

这只是一个非常基础的网络编程示例。在实际应用中，你可能需要处理多个客户端连接、使用非阻塞I/O、实现更复杂的协议等。对于这些高级主题，你可能需要学习更多关于select、poll、epoll、线程和进程的知识。

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