用cplusplus语言举例说明通信中的三次握手程序代码

以下是使用C++语言实现的基本的三次握手程序代码：

客户端代码：

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

using namespace std;

int main(int argc, char *argv[]) {
    const char *server_address = "127.0.0.1";
    int server_port = 8888;

    // 创建套接字
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) {
        cerr << "Failed to create socket." << endl;
        return -1;
    }

    // 连接服务器
    struct sockaddr_in server_addr;
    bzero(&server_addr, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(server_port);
    inet_pton(AF_INET, server_address, &server_addr.sin_addr);
    if (connect(sockfd, (struct sockaddr *) &server_addr, sizeof(server_addr)) < 0) {
        cerr << "Failed to connect server." << endl;
        return -1;
    }

    // 发送SYN
    char syn_msg[] = "SYN";
    send(sockfd, syn_msg, strlen(syn_msg), 0);

    // 接收SYN+ACK
    char syn_ack_msg[10];
    recv(sockfd, syn_ack_msg, 10, 0);
    if (strncmp(syn_ack_msg, "SYN+ACK", 7) != 0) {
        cerr << "Error message received from server." << endl;
        return -1;
    }

    // 发送ACK
    char ack_msg[] = "ACK";
    send(sockfd, ack_msg, strlen(ack_msg), 0);

    // 关闭套接字
    close(sockfd);

    return 0;
}

服务端代码：

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

using namespace std;

int main(int argc, char *argv[]) {
    const char *server_address = "127.0.0.1";
    int server_port = 8888;

    // 创建套接字
    int listenfd = socket(AF_INET, SOCK_STREAM, 0);
    if (listenfd < 0) {
        cerr << "Failed to create socket." << endl;
        return -1;
    }

    // 绑定地址和端口
    struct sockaddr_in server_addr;
    bzero(&server_addr, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(server_port);
    inet_pton(AF_INET, server_address, &server_addr.sin_addr);
    if (bind(listenfd, (struct sockaddr *) &server_addr, sizeof(server_addr)) < 0) {
        cerr << "Failed to bind address and port." << endl;
        return -1;
    }

    // 监听连接
    if (listen(listenfd, 5) < 0) {
        cerr << "Failed to listen." << endl;
        return -1;
    }

    // 接收连接
    struct sockaddr_in client_addr;
    socklen_t client_addr_len = sizeof(client_addr);
    int connfd = accept(listenfd, (struct sockaddr *) &client_addr, &client_addr_len);
    if (connfd < 0) {
        cerr << "Failed to accept connection." << endl;
        return -1;
    }

    // 接收SYN
    char syn_msg[10];
    recv(connfd, syn_msg, 10, 0);
    if (strncmp(syn_msg, "SYN", 3) != 0) {
        cerr << "Error message received from client." << endl;
        return -1;
    }

    // 发送SYN+ACK
    char syn_ack_msg[] = "SYN+ACK";
    send(connfd, syn_ack_msg, strlen(syn_ack_msg), 0);

    // 接收ACK
    char ack_msg[10];
    recv(connfd, ack_msg, 10, 0);
    if (strncmp(ack_msg, "ACK", 3) != 0) {
        cerr << "Error message received from client." << endl;
        return -1;
    }

    // 关闭套接字
    close(connfd);
    close(listenfd);

    return 0;
}