请教UDP发送函数sendto的使用问题

请教UDP发送函数sendto的使用问题

给你一段简单处理的代码，你参考一下：
C/C++ code

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sockaddr_in sendAddr;
sendAddr.sin_family = AF_INET;
sendAddr.sin_addr.s_addr = INADDR_BROADCAST;
sendAddr.sin_port = htons(SDP_SERVER_PORT);

//组包头
CommunicateHeader header;

memset(&header, 0, sizeof(CommunicateHeader));
memcpy(&header.leadByte, "NVSP", sizeof(header.leadByte));
header.version = 0;
header.flag = 0;
header.sequense = 0;
header.dataLength =0;
header.cmmand = NVSP_UDP_DEVICE;
header.result = 0;

UINT iCheckSum = nvspchecksum((UCHAR*)(&header), sizeof(CommunicateHeader));

SOCKET sendSocket = socket(AF_INET, SOCK_DGRAM, 0);
if(INVALID_SOCKET == m_sdpSendSocket)
{
AfxMessageBox(_T("创建SOCKET失败！"));
return;
}

BOOL optval;
lRet=setsockopt(sendSocket, SOL_SOCKET, SO_BROADCAST, (LPSTR)&optval, sizeof(optval));//设定为广播形式
if(-1==lRet)
{
AfxMessageBox(_T("SOCKET选项设置失败！"));
return;
}

UINT bufferSize = sizeof(CommunicateHeader) + 4;
char* sendPacket = new char[bufferSize];
memcpy(sendPacket, &header, sizeof(CommunicateHeader));
memcpy(sendPacket + sizeof(CommunicateHeader), &iCheckSum, sizeof(iCheckSum));

long lBytesSend = sendto(sendSocket, (char*)sendPacket, bufferSize, 0, (LPSOCKADDR)&sendAddr,sizeof(sendAddr));
if (lBytesSend != bufferSize)
{
AfxMessageBox(_T("发送数据失败！"));
return -1;
}
delete []sendPacket;

应该不会阻塞，没有实际关注过。 待发送内容进入底层网络缓冲，网卡ready就会发出去。