pop3接收协议的简单代码c++

以下是简单的 POP3 接收邮件的 C++ 代码示例：

#include <iostream>
#include <string>
#include <winsock2.h>

#pragma comment(lib, "ws2_32.lib")

using namespace std;

#define BUF_SIZE 1024

int main()
{
    // 初始化 Winsock 库
    WSADATA wsaData;
    int err = WSAStartup(MAKEWORD(2, 2), &wsaData);
    if (err != 0) {
        cout << "WSAStartup failed: " << err << endl;
        return -1;
    }

    // 创建套接字
    SOCKET sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (sock == INVALID_SOCKET) {
        cout << "socket failed: " << WSAGetLastError() << endl;
        WSACleanup();
        return -1;
    }

    // 设置服务器地址和端口号
    sockaddr_in serverAddr;
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_addr.s_addr = inet_addr("邮件服务器地址");
    serverAddr.sin_port = htons(110);

    // 连接服务器
    err = connect(sock, (sockaddr*)&serverAddr, sizeof(serverAddr));
    if (err == SOCKET_ERROR) {
        cout << "connect failed: " << WSAGetLastError() << endl;
        closesocket(sock);
        WSACleanup();
        return -1;
    }

    // 接收服务器欢迎信息
    char buf[BUF_SIZE] = { 0 };
    err = recv(sock, buf, BUF_SIZE, 0);
    if (err == SOCKET_ERROR) {
        cout << "recv failed: " << WSAGetLastError() << endl;
        closesocket(sock);
        WSACleanup();
        return -1;
    }
    cout << buf << endl;

    // 发送用户名和密码
    string user = "用户名\r\n";
    string pass = "密码\r\n";
    err = send(sock, user.c_str(), user.length(), 0);
    if (err == SOCKET_ERROR) {
        cout << "send failed: " << WSAGetLastError() << endl;
        closesocket(sock);
        WSACleanup();
        return -1;
    }
    err = recv(sock, buf, BUF_SIZE, 0);
    if (err == SOCKET_ERROR) {
        cout << "recv failed: " << WSAGetLastError() << endl;
        closesocket(sock);
        WSACleanup();
        return -1;
    }
    cout << buf << endl;
    err = send(sock, pass.c_str(), pass.length(), 0);
    if (err == SOCKET_ERROR) {
        cout << "send failed: " << WSAGetLastError() << endl;
        closesocket(sock);
        WSACleanup();
        return -1;
    }
    err = recv(sock, buf, BUF_SIZE, 0);
    if (err == SOCKET_ERROR) {
        cout << "recv failed: " << WSAGetLastError() << endl;
        closesocket(sock);
        WSACleanup();
        return -1;
    }
    cout << buf << endl;

    // 发送 LIST 命令获取邮件列表
    string list = "LIST\r\n";
    err = send(sock, list.c_str(), list.length(), 0);
    if (err == SOCKET_ERROR) {
        cout << "send failed: " << WSAGetLastError() << endl;
        closesocket(sock);
        WSACleanup();
        return -1;
    }
    err = recv(sock, buf, BUF_SIZE, 0);
    if (err == SOCKET_ERROR) {
        cout << "recv failed: " << WSAGetLastError() << endl;
        closesocket(sock);
        WSACleanup();
        return -1;
    }
    cout << buf << endl;

    // 发送 RETR 命令获取指定邮件的内容
    string retr = "RETR 邮件编号\r\n";
    err = send(sock, retr.c_str(), retr.length(), 0);
    if (err == SOCKET_ERROR) {
        cout << "send failed: " << WSAGetLastError() << endl;
        closesocket(sock);
        WSACleanup();
        return -1;
    }
    err = recv(sock, buf, BUF_SIZE, 0);
    if (err == SOCKET_ERROR) {
        cout << "recv failed: " << WSAGetLastError() << endl;
        closesocket(sock);
        WSACleanup();
        return -1;
    }
    cout << buf << endl;

    // 发送 DELE 命令标记邮件为删除状态
    string dele = "DELE 邮件编号\r\n";
    err = send(sock, dele.c_str(), dele.length(), 0);
    if (err == SOCKET_ERROR) {
        cout << "send failed: " << WSAGetLastError() << endl;
        closesocket(sock);
        WSACleanup();
        return -1;
    }
    err = recv(sock, buf, BUF_SIZE, 0);
    if (err == SOCKET_ERROR) {
        cout << "recv failed: " << WSAGetLastError() << endl;
        closesocket(sock);
        WSACleanup();
        return -1;
    }
    cout << buf << endl;

    // 发送 QUIT 命令关闭连接
    string quit = "QUIT\r\n";
    err = send(sock, quit.c_str(), quit.length(), 0);
    if (err == SOCKET_ERROR) {
        cout << "send failed: " << WSAGetLastError() << endl;
        closesocket(sock);
        WSACleanup();
        return -1;
    }
    err = recv(sock, buf, BUF_SIZE, 0);
    if (err == SOCKET_ERROR) {
        cout << "recv failed: " << WSAGetLastError() << endl;
        closesocket(sock);
        WSACleanup();
        return -1;
    }
    cout << buf << endl;

    // 关闭连接
    closesocket(sock);
    WSACleanup();

    return 0;
}

注意：上述代码仅为参考，具体实现过程需要根据 POP3 协议规范进行调整。另外，需要将代码中的“邮件服务器地址”和“邮件编号”替换为实际的值。