前天写了一个基于tcp协议的服务器客户端程序,今天写了一个基于UDP协议的,由于在上一篇使用TCP协议的服务器中注释已经较为详细,且许多api的调用是相同的,故不再另外注释。
使用UDP协议需要注意几点：
①UDP是面向无连接的,客户端在于服务器通信前无须建立连接,且UDP协议不保证发出的消息是否被收到,是否有丢失。
②UDP的接收和发送信息使用recvfrom()与sendto()函数
代码如下:
服务器端:
1 #include <iostream> 2 #include "Ws2tcpip.h" 3 #include "Winsock2.h" 4 5 using std::cin; 6 using std::cout; 7 using std::cerr; 8 using std::endl; 9 10 #pragma comment(lib, "ws2_32.lib") 11 12 int SOCKADDR_IN_SIZE = sizeof(SOCKADDR_IN); 13 const u_short DEFAULT_PORT = 4000; 14 const size_t MSG_BUF_SIZE = 512; 15 const size_t IP_BUF_SIZE = 256; 16 17 int main() { 18 WSADATA wsa_data; 19 SOCKET sock_serv = INVALID_SOCKET; 20 SOCKADDR_IN addr_serv, addr_clt; 21 char ip_buf[IP_BUF_SIZE]; 22 char msg_buf[MSG_BUF_SIZE]; 23 int ret_val = 0; 24 // 25 ret_val = WSAStartup(MAKEWORD(2, 2), &wsa_data); 26 if (ret_val != 0) { 27 cerr << "WSAStartup() function failed with error: " << WSAGetLastError() << " "; 28 system("pause"); 29 return 1; 30 } 31 // 32 //SecureZeroMemory(&addr_serv, SOCKADDR_IN_SIZE); 33 addr_serv.sin_family = AF_INET; 34 addr_serv.sin_port = htons(DEFAULT_PORT); 35 addr_serv.sin_addr.S_un.S_addr = ADDR_ANY; 36 // 37 sock_serv = socket(addr_serv.sin_family, SOCK_DGRAM, IPPROTO_UDP); 38 if (sock_serv == INVALID_SOCKET) { 39 cerr << "socket() function failed with error: " << WSAGetLastError() << " "; 40 WSACleanup(); 41 system("pause"); 42 return 1; 43 } 44 // 45 ret_val = bind(sock_serv, (SOCKADDR*)&addr_serv, SOCKADDR_IN_SIZE); 46 if (ret_val != 0) { 47 cerr << "bind() function failed with error: " << WSAGetLastError() << " "; 48 system("pause"); 49 return 1; 50 } 51 cout << "A UDP server has started successfully..." << endl; 52 // 53 while (true) { 54 SecureZeroMemory(msg_buf, MSG_BUF_SIZE); 55 ret_val = recvfrom(sock_serv, msg_buf, MSG_BUF_SIZE, 0, (SOCKADDR*)&addr_clt, &SOCKADDR_IN_SIZE); 56 if (ret_val > 0) { 57 inet_ntop(addr_clt.sin_family, &addr_clt, ip_buf, IP_BUF_SIZE); 58 cout << "message from client " << ip_buf << ": " << msg_buf << endl; 59 cout << "enter the message to response: "; 60 cin.getline(msg_buf, MSG_BUF_SIZE); 61 sendto(sock_serv, msg_buf, strlen(msg_buf), 0, (SOCKADDR*)&addr_clt, SOCKADDR_IN_SIZE); 62 } 63 else if (ret_val == 0) { 64 cout << "connection is closed..." << endl; 65 } 66 else { 67 cerr << "recvfrom() function failed with error: " << WSAGetLastError() << " "; 68 closesocket(sock_serv); 69 WSACleanup(); 70 system("pause"); 71 return 1; 72 } 73 } 74 ret_val = shutdown(sock_serv, SD_BOTH); 75 if (ret_val == SOCKET_ERROR) { 76 cerr << "shutdown() function failed with error: " << WSAGetLastError() << " "; 77 closesocket(sock_serv); 78 WSACleanup(); 79 system("pause"); 80 return 1; 81 } 82 closesocket(sock_serv); 83 WSACleanup(); 84 cout << "server shutdown..." << endl; 85 system("pause"); 86 return 0; 87 }
客户端:
1 #include <Winsock2.h> 2 #include <WS2tcpip.h> 3 #include <iostream> 4 5 using std::cout; 6 using std::cin; 7 using std::cerr; 8 using std::endl; 9 10 #pragma comment(lib, "ws2_32.lib") 11 12 const int MSG_BUF_SIZE = 512; 13 int SOCKADDR_SIZE = sizeof(SOCKADDR); 14 const int SERV_PORT = 4000; 15 const char *SERV_IP = "127.0.0.1"; 16 17 int main() { 18 WSADATA wsa_data; 19 SOCKET sock_clt = INVALID_SOCKET; 20 SOCKADDR_IN addr_serv; 21 char msg_buf[MSG_BUF_SIZE]; 22 int ret_val = 0; 23 // 24 ret_val = WSAStartup(MAKEWORD(2, 2), &wsa_data); 25 if (ret_val != 0) { 26 cerr << "WSAStartup() function failed with error: " << WSAGetLastError() << " "; 27 system("pause"); 28 return 1; 29 } 30 // 31 sock_clt = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP); 32 if (sock_clt == INVALID_SOCKET) { 33 cerr << "socket() function failed with error: " << WSAGetLastError() << " "; 34 WSACleanup(); 35 system("pause"); 36 return 1; 37 } 38 // 39 addr_serv.sin_family = AF_INET; 40 addr_serv.sin_port = htons(SERV_PORT); 41 ret_val = InetPton(addr_serv.sin_family, SERV_IP, &addr_serv.sin_addr); 42 if (ret_val != 1) { 43 cerr << "inet_pton() function failed with error: " << WSAGetLastError() << " "; 44 closesocket(sock_clt); 45 WSACleanup(); 46 system("pause"); 47 return 1; 48 } 49 // 50 cout << "A UDP client has already started successfully..." << endl; 51 // 52 //SecureZeroMemory(msg_buf, MSG_BUF_SIZE); 53 while (true) { 54 cout << "enter the message you want to send: "; 55 cin.getline(msg_buf, MSG_BUF_SIZE); 56 ret_val = sendto(sock_clt, msg_buf, strlen(msg_buf), 0, (SOCKADDR*)&addr_serv, SOCKADDR_SIZE); 57 if (ret_val == SOCKET_ERROR) { 58 cerr << "sendto() function failed with error: " << WSAGetLastError() << " "; 59 closesocket(sock_clt); 60 WSACleanup(); 61 system("pause"); 62 return 1; 63 } 64 SecureZeroMemory(msg_buf, MSG_BUF_SIZE); 65 ret_val = recvfrom(sock_clt, msg_buf, MSG_BUF_SIZE, 0, (SOCKADDR*)&addr_serv, &SOCKADDR_SIZE); 66 if (ret_val > 0) { 67 cout << "feedback from the server: " << msg_buf << endl; 68 } 69 else if (ret_val == 0) { 70 cout << "connection is closed..." << endl; 71 } 72 else { 73 cerr << "recvfrom() function failed with error: " << WSAGetLastError() << " "; 74 closesocket(sock_clt); 75 WSACleanup(); 76 system("pause"); 77 return 1; 78 } 79 } 80 ret_val = shutdown(sock_clt, SD_BOTH); 81 if (ret_val == SOCKET_ERROR) { 82 cerr << "shutdown() function failed with error: " << WSAGetLastError() << " "; 83 closesocket(sock_clt); 84 WSACleanup(); 85 system("pause"); 86 return 1; 87 } 88 closesocket(sock_clt); 89 WSACleanup(); 90 system("pause"); 91 return 0; 92 }