Ubuntu环境下C++网络编程如何实现 - 问答

在Ubuntu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TCP服务器和客户端的示例，展示了如何在Ubuntu上使用C++进行网络编程。

1. 安装必要的库

首先，确保你已经安装了g++编译器和相关的库。如果没有安装，可以使用以下命令进行安装：

sudo apt update
sudo apt install g++

2. 编写TCP服务器代码

创建一个名为tcp_server.cpp的文件，并添加以下代码：

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

#define PORT 8080

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(PORT);

    // 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;
}

3. 编写TCP客户端代码

创建一个名为tcp_client.cpp的文件，并添加以下代码：

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

#define PORT 8080

int main() {
    struct sockaddr_in serv_addr;
    int sock = 0;
    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(PORT);

    // 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;
}

4. 编译和运行

使用g++编译服务器和客户端代码：

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

运行服务器：

./tcp_server

在另一个终端运行客户端：

./tcp_client

你应该会看到服务器和客户端之间的通信。

5. UDP服务器和客户端示例

如果你对UDP感兴趣，可以参考以下简单的UDP服务器和客户端示例。

UDP服务器代码（udp_server.cpp）

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

#define PORT 8080

int main() {
    int sockfd;
    struct sockaddr_in servaddr, cliaddr;
    char buffer[1024] = {0};

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

    memset(&servaddr, 0, sizeof(servaddr));
    memset(&cliaddr, 0, sizeof(cliaddr));

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

    bind(sockfd, (const struct sockaddr*)&servaddr, sizeof(servaddr));

    int n;
    socklen_t len = sizeof(cliaddr);
    n = recvfrom(sockfd, (char*)buffer, 1024, MSG_WAITALL, (struct sockaddr*)&cliaddr, &len);
    buffer[n] = '\0';
    std::cout << "Client message: " << buffer << std::endl;

    sendto(sockfd, (const char*)buffer, strlen(buffer), MSG_CONFIRM, (const struct sockaddr*)&cliaddr, len);

    close(sockfd);

    return 0;
}

UDP客户端代码（udp_client.cpp）

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

#define PORT 8080

int main() {
    int sockfd;
    struct sockaddr_in servaddr;

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

    memset(&servaddr, 0, sizeof(servaddr));

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

    const char* hello = "Hello from UDP client";
    sendto(sockfd, (const char*)hello, strlen(hello), MSG_CONFIRM, (const struct sockaddr*)&servaddr, sizeof(servaddr));

    char buffer[1024] = {0};
    int n = recvfrom(sockfd, (char*)buffer, 1024, MSG_WAITALL, (struct sockaddr*)&servaddr, NULL);
    buffer[n] = '\0';
    std::cout << "Server reply: " << buffer << std::endl;

    close(sockfd);

    return 0;
}

编译和运行UDP服务器和客户端的方法与TCP示例相同。

通过这些示例，你应该能够在Ubuntu环境下使用C++进行基本的网络编程。

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