1. TCP/IP 编程基本概念
- TCP（传输控制协议）：面向连接、可靠的传输层协议，保证数据顺序和完整性。
- IP（网际协议）：负责将数据包路由到目标地址。
- Socket（套接字）：网络通信的端点，通过IP和端口标识。
2. 服务器端实现步骤
步骤 1：创建套接字
#include <sys/socket.h>
#include <netinet/in.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <cstring>
#include <iostream>int main() {// 创建套接字int server_fd = socket(AF_INET, SOCK_STREAM, 0);if (server_fd == -1) {std::cerr << "Socket creation failed\n";return -1;}
步骤 2：绑定套接字到地址和端口
// 设置地址结构struct sockaddr_in address;address.sin_family = AF_INET; // IPv4address.sin_addr.s_addr = INADDR_ANY; // 绑定所有接口address.sin_port = htons(8080); // 端口号（需转为网络字节序）// 绑定套接字if (bind(server_fd, (struct sockaddr*)&address, sizeof(address)) < 0) {std::cerr << "Bind failed\n";return -1;}
步骤 3：监听连接请求
// 监听，队列长度设为5if (listen(server_fd, 5) < 0) {std::cerr << "Listen failed\n";return -1;}std::cout << "Server listening on port 8080...\n";
步骤 4：接受客户端连接
// 接受连接int addrlen = sizeof(address);int new_socket = accept(server_fd, (struct sockaddr*)&address, (socklen_t*)&addrlen);if (new_socket < 0) {std::cerr << "Accept failed\n";return -1;}std::cout << "Client connected\n";
步骤 5：接收和发送数据
// 接收数据char buffer[1024] = {0};int valread = read(new_socket, buffer, 1024);std::cout << "Received: " << buffer << std::endl;// 发送响应const char* response = "Hello from server";send(new_socket, response, strlen(response), 0);std::cout << "Response sent\n";
步骤 6：关闭套接字
close(new_socket);close(server_fd);return 0;
}
3. 客户端实现步骤
步骤 1：创建套接字
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <cstring>
#include <iostream>int main() {// 创建套接字int sock = socket(AF_INET, SOCK_STREAM, 0);if (sock == -1) {std::cerr << "Socket creation failed\n";return -1;}
步骤 2：设置服务器地址
struct sockaddr_in serv_addr;serv_addr.sin_family = AF_INET;serv_addr.sin_port = htons(8080); // 服务器端口// 将IP地址从字符串转为二进制格式if (inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr) <= 0) {std::cerr << "Invalid address\n";return -1;}
步骤 3：连接到服务器
if (connect(sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) < 0) {std::cerr << "Connection failed\n";return -1;}std::cout << "Connected to server\n";
步骤 4：发送和接收数据
// 发送数据const char* message = "Hello from client";send(sock, message, strlen(message), 0);std::cout << "Message sent\n";// 接收响应char buffer[1024] = {0};int valread = read(sock, buffer, 1024);std::cout << "Server response: " << buffer << std::endl;
步骤 5：关闭套接字
close(sock);return 0;
}
4. 关键函数和结构体
socket(): 创建套接字。bind(): 绑定套接字到地址和端口。listen(): 进入监听状态。accept(): 接受客户端连接。connect(): 客户端连接到服务器。send()/recv()或write()/read(): 发送和接收数据。sockaddr_in: 存储地址信息的结构体（IPv4）。
5. 注意事项
- 错误处理：每次调用网络函数后检查返回值。
- 字节序转换：
htons(): 主机字节序转网络字节序（端口）。inet_pton(): 字符串IP转二进制。
- 资源释放：使用
close()关闭套接字。 - 端口复用：通过
setsockopt()设置SO_REUSEADDR选项。
6. 完整示例代码
-
服务器端
#include <iostream> #include <sys/socket.h> #include <netinet/in.h> #include <unistd.h> #include <string.h>int main() {int server_fd, new_socket;struct sockaddr_in address;int addrlen = sizeof(address);char buffer[1024] = {0};const char* hello = "Hello from server";// 创建socketif ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0) {perror("socket failed");exit(EXIT_FAILURE);}// 绑定socketaddress.sin_family = AF_INET;address.sin_addr.s_addr = INADDR_ANY;address.sin_port = htons(8080);if (bind(server_fd, (struct sockaddr*)&address, sizeof(address)) < 0) {perror("bind failed");exit(EXIT_FAILURE);}// 监听socketif (listen(server_fd, 3) < 0) {perror("listen");exit(EXIT_FAILURE);}// 接受连接if ((new_socket = accept(server_fd, (struct sockaddr*)&address, (socklen_t*)&addrlen)) < 0) {perror("accept");exit(EXIT_FAILURE);}// 读取客户端发送的数据read(new_socket, buffer, 1024);std::cout << "Message from client: " << buffer << std::endl;// 向客户端发送数据send(new_socket, hello, strlen(hello), 0);std::cout << "Hello message sent\n";// 关闭socketclose(new_socket);close(server_fd);return 0; } #include <iostream> #include <sys/socket.h> #include <netinet/in.h> #include <unistd.h> #include <string.h>int main() {int server_fd, new_socket;struct sockaddr_in address;int addrlen = sizeof(address);char buffer[1024] = {0};const char* hello = "Hello from server";// 创建socketif ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0) {perror("socket failed");exit(EXIT_FAILURE);}// 绑定socketaddress.sin_family = AF_INET;address.sin_addr.s_addr = INADDR_ANY;address.sin_port = htons(8080);if (bind(server_fd, (struct sockaddr*)&address, sizeof(address)) < 0) {perror("bind failed");exit(EXIT_FAILURE);}// 监听socketif (listen(server_fd, 3) < 0) {perror("listen");exit(EXIT_FAILURE);}// 接受连接if ((new_socket = accept(server_fd, (struct sockaddr*)&address, (socklen_t*)&addrlen)) < 0) {perror("accept");exit(EXIT_FAILURE);}// 读取客户端发送的数据read(new_socket, buffer, 1024);std::cout << "Message from client: " << buffer << std::endl;// 向客户端发送数据send(new_socket, hello, strlen(hello), 0);std::cout << "Hello message sent\n";// 关闭socketclose(new_socket);close(server_fd);return 0; } -
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;char buffer[1024] = {0};const char* hello = "Hello from client";// 创建socketif ((sock = socket(AF_INET, SOCK_STREAM, 0)) < 0) {std::cerr << "Socket creation error" << std::endl;return -1;}// 设置服务器地址serv_addr.sin_family = AF_INET;serv_addr.sin_port = htons(8080);// 将IP地址从字符串转换为网络格式if (inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr) <= 0) {std::cerr << "Invalid address/Address not supported" << std::endl;return -1;}// 连接到服务器if (connect(sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) < 0) {std::cerr << "Connection Failed" << std::endl;return -1;}// 向服务器发送数据send(sock, hello, strlen(hello), 0);std::cout << "Hello message sent" << std::endl;// 读取服务器发送的数据read(sock, buffer, 1024);std::cout << "Message from server: " << buffer << std::endl;// 关闭socketclose(sock);return 0; }
编译运行：
# 编译服务器
g++ server.cpp -o server
# 编译客户端
g++ client.cpp -o client# 启动服务器
./server
# 启动客户端（另起终端）
./client
对于更复杂的场景（如多客户端并发），需结合多线程或异步I/O（如 select/epoll）进行扩展。
