### UDP

一、说明
使用UDP时，直接使用API代替控件。

第一个程序(ReadBufferUdp)使用来接收到缓存中。

"Destino"变量非常重要，如果你从其他地方接收数据到Buffer，你必须设置Destino = 0 并且在以后执行的时候赋值你将要发送的包的地址给它（after the execution it will have the address which send you the packet.）。
如果你只想从一个指定的地址接收数据，你必须设置变量Destino = <address>.

"gvEncerrar" 用来中止处理过程。(gvEncerrar被设置为全局变量。)

超时时间设置。"Inicio + 12" = 12 sec of timeout.
第三个程序是用来准备WinSock程序。

二、代码

int ReadBufferUdp(unsigned long *Destino,void *T,int Size)
{
char Buffer[128];
SOCKADDR_IN SockAddr;
int LenSockAddr=sizeof(SOCKADDR_IN);
fd_set FdRead;
struct timeval t_val;
int Ret;
time_t Inicio = time(NULL);

Application->ProcessMessages();
if(gvEncerrar)
return false;

FD_ZERO(&FdRead);
FD_SET(gvSocket,&FdRead);
t_val.tv_sec=0;
t_val.tv_usec=0;

while((Ret=select(0,&FdRead,NULL,NULL,&t_val))!=1 && (Inicio + 12) >
time(NULL) && !gvEncerrar)
{
FD_ZERO(&FdRead);
FD_SET(gvSocket,&FdRead);
t_val.tv_sec=0;
t_val.tv_usec=0;
Application->ProcessMessages();
}
if(Ret != 1)
return false;

if(recvfrom(gvSocket,Buffer,Size,0,(LPSOCKADDR)&SockAddr,&LenSockAddr)!=Size)

return false;

if(*Destino == 0)
{
*Destino = SockAddr.sin_addr.s_addr;
}
else
if(*Destino != SockAddr.sin_addr.s_addr)
return false;

memcpy(T,Buffer,Size);
return true;
}

int WriteBufferUdp(unsigned long Destino,void *T,int Size)
{
SOCKADDR_IN SockAddr;
int Sent;

Application->ProcessMessages();
SockAddr.sin_family = AF_INET;
SockAddr.sin_port = gvPortUdp;
SockAddr.sin_addr.s_addr = Destino;
Sent = sendto(gvSocket,(char
*)T,Size,0,(LPSOCKADDR)&SockAddr,sizeof(SockAddr));
if(Sent != Size)
return false;
else
return true;
}

void InicializaTCPIP()
{

WORD wVersionRequested;
WSADATA wsaData;
IN_ADDR In;
PSERVENT PServent;
SOCKADDR_IN SockAddrIn;
wVersionRequested = MAKEWORD( 1, 1 );

if(WSAStartup( wVersionRequested, &wsaData ))
{
ShowMessage("Erro na inicializao do TCP/IP");
Application->Terminate();
return;
}

// Get the port on service file
if((PServent=getservbyname("your_service_name","udp"))==NULL)
{
ShowMessage("Erro obtendo port do servi transurb/udp");
Application->Terminate();
return;
}
gvPortUdp = PServent->s_port;
sprintf(StrAux,"Servi transurb/udp port:%d",ntohs(gvPortUdp));
Log(StrAux);

// Open de Socket
if((gvSocket = socket(AF_INET,SOCK_DGRAM,0))==INVALID_SOCKET)
{
ShowMessage("Erro na criao do socket");
Application->Terminate();
return;
}
Log("Socket criado com sucesso");

// Do the bind
SockAddrIn.sin_family = AF_INET;
SockAddrIn.sin_port = gvPortUdp;
SockAddrIn.sin_addr.s_addr = NULL;

if(bind(gvSocket,(LPSOCKADDR)&SockAddrIn,sizeof(SockAddrIn))==SOCKET_ERROR)

{
ShowMessage("Erro no bind do socket");
Application->Terminate();
return;
}
Log("Bind do socket com sucesso");

}