From: Ralph Mason <ralph.mason@...>
Date: 2002-01-11T07:13:11+09:00
Subject: Something ODD with UDPSocket - Five second wait?

Here is an odd thing, so odd that I am sure it must be something I am doing
wrong.

I am using UDP to debug a remote application.  So I think, couple of lines
of ruby and I have my tracer. But I run into a problem, it takes about 5
seconds from when I send the data (from C) for it to be printed by ruby.
This does not happen if I send it from ruby - how odd.

----------------------------------------

require "socket"

sock = UDPSocket.open
sock.bind("",2600)

while true
  p sock.recvfrom(512)
end

----------------------------------------

So far so good, all works fine.

I test it with some more ruby, and the data is printed instantly

----------------------------------------

require "socket"

UDPSocket.open.send("Test debug",0,'localhost',2600)

----------------------------------------

Works fine.    So I start sending to it from C, and it takes 5 seconds for
the data to appear!!

I cant figure this out.  Here is the C I am using to send to the ruby
tracer.

----------------------------------------
int main(int argc, char* argv[])
{
 WSADATA wsaData;
 WSAStartup( MAKEWORD( 1,1 ), &wsaData );

 const char*  buff="Testing 1..2..3";

 SOCKET s=socket(AF_INET,SOCK_DGRAM,0);

 sockaddr_in addr;
 memset(&addr,0,sizeof(addr));

 addr.sin_family = AF_INET;
 addr.sin_port=htons(2600);
 addr.sin_addr.S_un.S_addr=inet_addr("192.168.1.1");

 sendto(s,(char*)buff,strlen(buff),0,(sockaddr *)&addr,sizeof(addr));

 return 0;
}
----------------------------------------

So I think, perhaps it's somethign to do with my machine. and write the a C
tracer program.  This one works as I expected the ruby app to work. (and
also goes to show why I wanted to write it in ruby :-)

----------------------------------------

int main(int argc, char* argv[])
{
 WSADATA wsaData;
 WSAStartup( MAKEWORD( 1,1 ), &wsaData );

 SOCKET s=socket(AF_INET,SOCK_DGRAM,0);

 sockaddr_in addr;
 memset(&addr,0,sizeof(addr));

 addr.sin_family = AF_INET;
 addr.sin_port=htons(2600);
 addr.sin_addr.S_un.S_addr=INADDR_ANY;

 if ( bind(s,(sockaddr*)&addr,sizeof(addr)) == 0 )
  while(1)
  {
   char buff[512];  ;

   int i= recvfrom(s,buff,512,0,NULL,NULL);

   if ( i == SOCKET_ERROR  )
   {
    printf("Error in recvfrom %d\n",WSAGetLastError());
    break;
   }

   buff[i]=0;
   printf("%s\n",buff);
  }
  else
   puts("Failed to bind");

 return 0;
}
----------------------------------------

Can anyone help with this?  Has anyone seen this problem before?


Thanks
Ralph