1 #include"winsock2.h" 2 #include<iostream> 3 using namespace std; 4 //This line is very important 5  6 #pragma comment(lib,"ws2_32.lib") 7 int main() 8 { 9     WSADATA              wsaData;10     SOCKET               ReceivingSocket;11     SOCKADDR_IN          ReceiverAddr;12     int                  Port = 5150;13     char                 ReceiveBuf[1024];14     int                  BufLength = 1024;15     SOCKADDR_IN          SenderAddr;16     int                  SenderAddrSize = sizeof(SenderAddr);17     int                  Ret;18 19     if ((Ret = WSAStartup(MAKEWORD(2,2), &wsaData)) != 0)20     {21         cout<<"WSAStartup failed with error "<<Ret<<endl;22         //here no WSACleanup，because we do not create anything;23         return -1;24     }25 26     // Create a new socket to listening for client connections.27     //Note the difference with TCP28     ReceivingSocket = socket(AF_INET,SOCK_DGRAM,IPPROTO_UDP);29     if ( INVALID_SOCKET == ReceivingSocket)30     {31         cout<<"Socket failed with error "<<WSAGetLastError()<<endl;32         WSACleanup();33         return -1;34     }35 36     ReceiverAddr.sin_family = AF_INET;37     ReceiverAddr.sin_addr.s_addr = htonl(INADDR_ANY);38     ReceiverAddr.sin_port = htons(Port);39 40     //to bind41     if (bind(ReceivingSocket, (SOCKADDR *)&ReceiverAddr, sizeof(ReceiverAddr)) == SOCKET_ERROR)42     {43         cout<<"Binding failed with error "<<WSAGetLastError()<<endl;44         closesocket(ReceivingSocket);45         WSACleanup();46         return -1;47     }48 49     // Listen for client connections. We used a backlog of 5 which is50     // normal for many applications.51 52     cout<<"** We are ready to receive 1 datagram from any interface on port "<<Port<<"**"<<endl;53 54     //accep a connection when one arrives55 56     57     58     cout<<"** We are waiting for data...**\n";59     //SenderAddrSize = sizeof(SenderAddr);60     Ret = recvfrom(ReceivingSocket,ReceiveBuf,BufLength,0,(SOCKADDR *)&SenderAddr,&SenderAddrSize);61     if (SOCKET_ERROR == Ret)62     {63         cout<<"Recvfrom failed with error "<<WSAGetLastError()<<endl;64         closesocket(ReceivingSocket);65         WSACleanup();66         return -1;67     }68     cout<<"**We have successfully recieve "<<Ret<<" Byte(s) data!**\n";69 70     cout<<"**We are going to close the client connection...**\n";71 72     closesocket(ReceivingSocket);73     WSACleanup();74 75     return 0;76 }

 1 #include"winsock2.h" 2 #include<iostream> 3  #include <time.h> 4 using namespace std; 5 //This line is very important 6  7 #pragma comment(lib,"ws2_32.lib") 8 int main(int argc, char **argv) 9 {10     WSADATA              wsaData;11     SOCKET               SendingSocket;12     SOCKADDR_IN          ReceiverAddr;13     int                  Port = 5150;14     int                  Ret;15 16     if (argc <= 1)17     {18         cout<<"USAGE: udpclient <Server IP address>.\n";19         return -1;20     }21 22     // Initialize Winsock version 2.223 24     if ((Ret = WSAStartup(MAKEWORD(2,2), &wsaData)) != 0)25     {26         cout<<"WSAStartup failed with error "<<Ret<<endl;27         return -1;28     }29 30     // Create a new socket to make a client connection.31 32     SendingSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);//Note the difference with TCP33     if (INVALID_SOCKET == SendingSocket)34     {35         cout << "socket failed with error " << WSAGetLastError()<<endl;36         WSACleanup();37         return -1;38     }39 40     ReceiverAddr.sin_family = AF_INET;41     ReceiverAddr.sin_port = htons(Port);    42     ReceiverAddr.sin_addr.s_addr = inet_addr(argv[1]);43 44     // Make a connection to the server with socket s.45 46     cout<< "We are trying to connect to " << inet_ntoa(ReceiverAddr.sin_addr)47         << ":" << htons(ReceiverAddr.sin_port) << "...\n";48 49     cout << "We will now try to send a hello message.\n";50         51     if ((Ret = sendto(SendingSocket, "Hello", 5, 0, (SOCKADDR *)&ReceiverAddr,sizeof(ReceiverAddr))) == SOCKET_ERROR)52     {53         cout << "Sendto failed with error " << WSAGetLastError()<<endl;54         closesocket(SendingSocket);55         WSACleanup();56         return -1;57     }58     59     cout << "We successfully sent " << Ret << " byte(s).\n";60     61     // When you are finished sending and receiving data on socket s,62     // you should close the socket.63 64     cout << "We are closing the connection.\n";65 66     closesocket(SendingSocket);67 68     // When your application is finished handling the connection, call69     // WSACleanup.70 71     WSACleanup();72     return 0;73 }