1. TCP/IP 編程基本概念
- TCP(傳輸控制協議):面向連接、可靠的傳輸層協議,保證數據順序和完整性。
- IP(網際協議):負責將數據包路由到目標地址。
- Socket(套接字):網絡通信的端點,通過IP和端口標識。
2. 服務器端實現步驟
步驟 1:創建套接字
#include <sys/socket.h>
#include <netinet/in.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <cstring>
#include <iostream>int main() {// 創建套接字int server_fd = socket(AF_INET, SOCK_STREAM, 0);if (server_fd == -1) {std::cerr << "Socket creation failed\n";return -1;}
步驟 2:綁定套接字到地址和端口
// 設置地址結構struct sockaddr_in address;address.sin_family = AF_INET; // IPv4address.sin_addr.s_addr = INADDR_ANY; // 綁定所有接口address.sin_port = htons(8080); // 端口號(需轉為網絡字節序)// 綁定套接字if (bind(server_fd, (struct sockaddr*)&address, sizeof(address)) < 0) {std::cerr << "Bind failed\n";return -1;}
步驟 3:監聽連接請求
// 監聽,隊列長度設為5if (listen(server_fd, 5) < 0) {std::cerr << "Listen failed\n";return -1;}std::cout << "Server listening on port 8080...\n";
步驟 4:接受客戶端連接
// 接受連接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";
步驟 5:接收和發送數據
// 接收數據char buffer[1024] = {0};int valread = read(new_socket, buffer, 1024);std::cout << "Received: " << buffer << std::endl;// 發送響應const char* response = "Hello from server";send(new_socket, response, strlen(response), 0);std::cout << "Response sent\n";
步驟 6:關閉套接字
close(new_socket);close(server_fd);return 0;
}
3. 客戶端實現步驟
步驟 1:創建套接字
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <cstring>
#include <iostream>int main() {// 創建套接字int sock = socket(AF_INET, SOCK_STREAM, 0);if (sock == -1) {std::cerr << "Socket creation failed\n";return -1;}
步驟 2:設置服務器地址
struct sockaddr_in serv_addr;serv_addr.sin_family = AF_INET;serv_addr.sin_port = htons(8080); // 服務器端口// 將IP地址從字符串轉為二進制格式if (inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr) <= 0) {std::cerr << "Invalid address\n";return -1;}
步驟 3:連接到服務器
if (connect(sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) < 0) {std::cerr << "Connection failed\n";return -1;}std::cout << "Connected to server\n";
步驟 4:發送和接收數據
// 發送數據const char* message = "Hello from client";send(sock, message, strlen(message), 0);std::cout << "Message sent\n";// 接收響應char buffer[1024] = {0};int valread = read(sock, buffer, 1024);std::cout << "Server response: " << buffer << std::endl;
步驟 5:關閉套接字
close(sock);return 0;
}
4. 關鍵函數和結構體
socket()
: 創建套接字。bind()
: 綁定套接字到地址和端口。listen()
: 進入監聽狀態。accept()
: 接受客戶端連接。connect()
: 客戶端連接到服務器。send()
/recv()
或write()
/read()
: 發送和接收數據。sockaddr_in
: 存儲地址信息的結構體(IPv4)。
5. 注意事項
- 錯誤處理:每次調用網絡函數后檢查返回值。
- 字節序轉換:
htons()
: 主機字節序轉網絡字節序(端口)。inet_pton()
: 字符串IP轉二進制。
- 資源釋放:使用
close()
關閉套接字。 - 端口復用:通過
setsockopt()
設置SO_REUSEADDR
選項。
6. 完整示例代碼
-
服務器端
#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";// 創建socketif ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0) {perror("socket failed");exit(EXIT_FAILURE);}// 綁定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);}// 監聽socketif (listen(server_fd, 3) < 0) {perror("listen");exit(EXIT_FAILURE);}// 接受連接if ((new_socket = accept(server_fd, (struct sockaddr*)&address, (socklen_t*)&addrlen)) < 0) {perror("accept");exit(EXIT_FAILURE);}// 讀取客戶端發送的數據read(new_socket, buffer, 1024);std::cout << "Message from client: " << buffer << std::endl;// 向客戶端發送數據send(new_socket, hello, strlen(hello), 0);std::cout << "Hello message sent\n";// 關閉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";// 創建socketif ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0) {perror("socket failed");exit(EXIT_FAILURE);}// 綁定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);}// 監聽socketif (listen(server_fd, 3) < 0) {perror("listen");exit(EXIT_FAILURE);}// 接受連接if ((new_socket = accept(server_fd, (struct sockaddr*)&address, (socklen_t*)&addrlen)) < 0) {perror("accept");exit(EXIT_FAILURE);}// 讀取客戶端發送的數據read(new_socket, buffer, 1024);std::cout << "Message from client: " << buffer << std::endl;// 向客戶端發送數據send(new_socket, hello, strlen(hello), 0);std::cout << "Hello message sent\n";// 關閉socketclose(new_socket);close(server_fd);return 0; }
-
客戶端:
#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";// 創建socketif ((sock = socket(AF_INET, SOCK_STREAM, 0)) < 0) {std::cerr << "Socket creation error" << std::endl;return -1;}// 設置服務器地址serv_addr.sin_family = AF_INET;serv_addr.sin_port = htons(8080);// 將IP地址從字符串轉換為網絡格式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;}// 連接到服務器if (connect(sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) < 0) {std::cerr << "Connection Failed" << std::endl;return -1;}// 向服務器發送數據send(sock, hello, strlen(hello), 0);std::cout << "Hello message sent" << std::endl;// 讀取服務器發送的數據read(sock, buffer, 1024);std::cout << "Message from server: " << buffer << std::endl;// 關閉socketclose(sock);return 0; }
編譯運行:
# 編譯服務器
g++ server.cpp -o server
# 編譯客戶端
g++ client.cpp -o client# 啟動服務器
./server
# 啟動客戶端(另起終端)
./client
對于更復雜的場景(如多客戶端并發),需結合多線程或異步I/O(如 select
/epoll
)進行擴展。