C++.IP协议通信

1. TCP协议通信

1.1 服务端实现

创建套接字

使用socket(AF_INET, SOCK_STREAM, 0)创建TCP套接字。其中，AF_INET表示使用IPv4协议族，SOCK_STREAM表示使用TCP协议，0表示让系统自动选择默认的协议。

int listenfd = socket(AF_INET, SOCK_STREAM, 0);
if (listenfd == -1) {perror("socket creation failed");exit(EXIT_FAILURE);
}

绑定地址

通过bind将套接字绑定到本地地址和端口。绑定时需要指定本地的IP地址和端口号，通常使用INADDR_ANY表示绑定到所有可用的网络接口。

struct sockaddr_in server_addr;
memset(&server_addr, 0, sizeof(server_addr));
server_addr.sin_family = AF_INET;
server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
server_addr.sin_port = htons(8080);if (bind(listenfd, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1) {perror("bind failed");exit(EXIT_FAILURE);
}

监听连接

调用listen函数开始监听客户端连接请求。listen函数的第二个参数backlog表示等待连接的队列长度，通常设置为SOMAXCONN。

if (listen(listenfd, SOMAXCONN) == -1) {perror("listen failed");exit(EXIT_FAILURE);
}

接受连接

使用accept函数接受客户端连接，返回新的套接字用于通信。accept函数会阻塞，直到有客户端连接请求到达。

struct sockaddr_in client_addr;
socklen_t client_len = sizeof(client_addr);
int clientfd = accept(listenfd, (struct sockaddr*)&client_addr, &client_len);
if (clientfd == -1) {perror("accept failed");exit(EXIT_FAILURE);
}

数据传输

通过send和recv函数与客户端进行数据交互。send函数用于向客户端发送数据，recv函数用于从客户端接收数据。

char buffer[1024];
memset(buffer, 0, sizeof(buffer));
int bytes_received = recv(clientfd, buffer, sizeof(buffer), 0);
if (bytes_received > 0) {printf("Received data: %s\n", buffer);send(clientfd, buffer, bytes_received, 0);
} else {perror("recv failed");
}

关闭连接

通信结束后调用close关闭套接字。

close(clientfd);
close(listenfd);

1.2 客户端实现

创建套接字

使用socket(AF_INET, SOCK_STREAM, 0)创建TCP套接字。

int clientfd = socket(AF_INET, SOCK_STREAM, 0);
if (clientfd == -1) {perror("socket creation failed");exit(EXIT_FAILURE);
}

连接服务器

通过connect函数向服务器发起连接请求。需要指定服务器的IP地址和端口号。

struct sockaddr_in server_addr;
memset(&server_addr, 0, sizeof(server_addr));
server_addr.sin_family = AF_INET;
server_addr.sin_port = htons(8080);
server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");if (connect(clientfd, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1) {perror("connect failed");exit(EXIT_FAILURE);
}

数据传输

使用send和recv函数与服务器进行数据交互。

char send_buffer[] = "Hello, Server!";
send(clientfd, send_buffer, strlen(send_buffer), 0);char recv_buffer[1024];
memset(recv_buffer, 0, sizeof(recv_buffer));
int bytes_received = recv(clientfd, recv_buffer, sizeof(recv_buffer), 0);
if (bytes_received > 0) {printf("Received data: %s\n", recv_buffer);
} else {perror("recv failed");
}

关闭连接

通信结束后调用close关闭套接字。

close(clientfd);

1.3 示例代码

服务端代码示例

#include <iostream>
#include <cstring>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>using namespace std;int main() {int listenfd = socket(AF_INET, SOCK_STREAM, 0);if (listenfd == -1) {perror("socket creation failed");exit(EXIT_FAILURE);}struct sockaddr_in server_addr;memset(&server_addr, 0, sizeof(server_addr));server_addr.sin_family = AF_INET;server_addr.sin_addr.s_addr = htonl(INADDR_ANY);server_addr.sin_port = htons(8080);if (bind(listenfd, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1) {perror("bind failed");exit(EXIT_FAILURE);}if (listen(listenfd, SOMAXCONN) == -1) {perror("listen failed");exit(EXIT_FAILURE);}struct sockaddr_in client_addr;socklen_t client_len = sizeof(client_addr);int clientfd = accept(listenfd, (struct sockaddr*)&client_addr, &client_len);if (clientfd == -1) {perror("accept failed");exit(EXIT_FAILURE);}char buffer[1024];memset(buffer, 0, sizeof(buffer));int bytes_received = recv(clientfd, buffer, sizeof(buffer), 0);if (bytes_received > 0) {printf("Received data: %s\n", buffer);send(clientfd, buffer, bytes_received, 0);} else {perror("recv failed");}close(clientfd);close(listenfd);return 0;
}

客户端代码示例

#include <iostream>