Windows网络编程（基础篇2）

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无连接通信UDP

无连接通信是通过UDP/IP协议完成的。UDP不能确保可靠的数据传输，但能将数据发送到过个目标，或者接收多个源数据。

UDP通信不用调用listen和accept。接收函数有recvfrom，和WSARecvFrom。

int recvfrom( _In_        SOCKET          s, _Out_       char            *buf, _In_        int             len, _In_        int             flags,//一般填0，具体看MSDN _Out_       struct sockaddr *from,//返回接收端的地址信息 _Inout_opt_ int             *fromlen //指向地址结构的长度);

int WSARecvFrom( _In_    SOCKET                             s, _Inout_ LPWSABUF                           lpBuffers, _In_    DWORD                              dwBufferCount, _Out_   LPDWORD                            lpNumberOfBytesRecvd, _Inout_ LPDWORD                            lpFlags, _Out_   struct sockaddr                    *lpFrom, _Inout_ LPINT                              lpFromlen, _In_    LPWSAOVERLAPPED                    lpOverlapped, _In_    LPWSAOVERLAPPED_COMPLETION_ROUTINE lpCompletionRoutine);

UDP接收端应用程序

#include<winsock2.h>#include<Ws2tcpip.h>#pragma comment(lib,"WS2_32")int main(void){WSADATA wsaData;SOCKET  receivingSocket;SOCKADDR_IN  ReceiverAddr;int Port = 5150;char ReceiveBuf[1024];int BufLength = 1024;SOCKADDR_IN SenderAddr;int SenderAddrSize = sizeof(SenderAddr);WSAStartup(MAKEWORD(2, 2), &wsaData);//创建一个新的套接字来接收数据报receivingSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);//建立一个SOCKADDR_IN结构，这个结构将告知我们想要使用5150端口来接收来自所有接口的数据报ReceiverAddr.sin_family = AF_INET;ReceiverAddr.sin_port = htons(Port);inet_pton(AF_INET, INADDR_ANY, (void*)&ReceiverAddr.sin_addr.S_un.S_addr);//使用bind将这个地址信息和套接字关联起来bind(receivingSocket, (SOCKADDR*)&SenderAddr, sizeof(SenderAddr));//此时可以在绑定套接字上接收数据报了recvfrom(receivingSocket, ReceiveBuf, BufLength, 0, (SOCKADDR*)&SenderAddr, &SenderAddrSize);//应用程序接收完数据报后。关闭套接字closesocket(receivingSocket);WSACleanup();return 1;}

发送函数有sendto，和WSASendto。

int sendto( _In_       SOCKET                s,        //socket描述符 _In_ const char                  *buf, //数据报缓存地址 _In_       int                   len,      //数据报长度 _In_       int                   flags,    //该参数一般为0 _In_       const struct sockaddr *to,      //数据发往哪里 _In_       int                   tolen //对方地址长度);//返回发送的字节数

int WSASendTo( _In_  SOCKET                             s, _In_  LPWSABUF                           lpBuffers, _In_  DWORD                              dwBufferCount, _Out_ LPDWORD                            lpNumberOfBytesSent, _In_  DWORD                              dwFlags, _In_  const struct sockaddr              *lpTo, _In_  int                                iToLen, _In_  LPWSAOVERLAPPED                    lpOverlapped, _In_  LPWSAOVERLAPPED_COMPLETION_ROUTINE lpCompletionRoutine);

UDP发送端示例：

WSADATA wsaData;SOCKET SendingSocket;SOCKADDR_IN ReceiverAddr;int Port = 5150;char SendBuf[1024];int BufLength = 1024;WSAStartup(MAKEWORD(2, 2), &wsaData);SendingSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);ReceiverAddr.sin_family = AF_INET;ReceiverAddr.sin_port = htons(Port);inet_pton(AF_INET, "136.149.3.29", (void*)&ReceiverAddr);sendto(SendingSocket, SendBuf, BufLength, 0, (SOCKADDR*)&ReceiverAddr, sizeof(ReceiverAddr));closesocket(SendingSocket);WSACleanup();

常用winsock API。

获取通信方的套接字地址信息，该信息是关于已建立连接的套接字。

int getpeername( _In_    SOCKET          s,     //准备连接的套接字 _Out_   struct sockaddr *name, _Inout_ int             *namelen);

获取给定套接字本地接口信息。

int getsockname( _In_    SOCKET          s, _Out_   struct sockaddr *name, _Inout_ int             *namelen);

声明：以上整理于Windows网络编程（第二版）

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