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Winsock connect() timeout - how to set?

Posted on 1998-10-05
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Last Modified: 2008-02-26
Does anyone know how to set the timeout when doing a Windows Socket connect()?

I can set the timeout on send() or recv() by calling select() first, but you need to be connected before select() works.

So how to set the timeout when trying to connect()?

Thanks,
NC
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Question by:nchenkin
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7 Comments
 
LVL 6

Expert Comment

by:snoegler
ID: 1253358
Just a thought:
Perhaps you could create a thread which calls connect(), and then timeout this thread:
(pseudocode):

int mythread()
{
  return connect();
}

myfunc()
{
.
  BeginThread(mythread);
  if(WaitForSingleObject(mythread, TIMEOUT)!=WAIT_OBJECT_0) {
    TerminateThread(mythread);
    // timeout ...
  } else
  {
    SOCKET sock=GetResultCode(mythread);
  }
}
0
 
LVL 3

Expert Comment

by:elfie
ID: 1253359
You can use the alarm call, combined with an interrupt handler.
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LVL 4

Accepted Solution

by:
jos010697 earned 400 total points
ID: 1253360
The funny thing is that one can set read/write timeout values, but no connect
timeout values for a socket. There's a way out though:

-- set the socket to nonblocking:

   int noblock= 1;
   ioctl(socket, FIONBIO, &noblock);

- connect the socket:

   struct sockaddr_in sin;
   int retval= connect(socket,  &sin sizeof(sin));

- if the connect succeeds (immediately, that is), nothing needs to be done;
  otherwise, if connect returned -1 and errno is set to EINPROGRESS,
  the socket is still busy connecting. A select() call can be performed
  (check if it is ready for writing).

The select call _does_ have a user definable timeout value (it's the last parameter)
and voila, there you've got what you want.

kind regards,

Jos aka jos@and.nl

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Author Comment

by:nchenkin
ID: 1253361
snoegler and elfie,

Thanks for your comments. I had forgot to mention that I was using blocking sockets, but jos realized that. I think his answer is what I was looking for.

jos,

That looks like a good solution. I'll test it out today or tomorrow, but the points are yours for now!

Thanks,
Nelson


0
 

Author Comment

by:nchenkin
ID: 1253362
jos,

Actually, I have one more question if you don't mind. After doing the initial connect, then can you set the socket back in blocking? So the sequence is:

Set to non-blocking with ioctl()
Connect
Set to blocking with iotcl()
Select with timeout
Communicate with client or handle timeout error...

Does that look OK?

Thanks,
NC
0
 
LVL 4

Expert Comment

by:jos010697
ID: 1253363
No, set the socket back to blocking mode _after_ the select has returned
succesfully (you're sure the connect has completed then). I really don't
have any idea what would happen if you'd do it the way you described ...

kind regards,

Jos aka jos@and.nl
0
 

Author Comment

by:nchenkin
ID: 1253364
jos,

Thanks for your now ancient response. The day it arrived I was on a plane heading off for 5 weeks of trekking in the Himalayas. Just back in the office today and wanted to acknowledge your resonse.

Actually, I think I implemented it the way I mentioned above and it <seems> to be working, but will probably change to your suggestion.

NC
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