Timeout on TCP Connection Attempt

Question

In C# I'm trying to test connectivity to a port like this:

Socket socket = new Socket(AddressFamily.InterNetwork,
                    SocketType.Stream,
                    ProtocolType.Tcp);

socket.Connect(telco.Address, telco.Port);

It works great when the port is available. However when the port is not available (e.g. google.com on TCP/81) it takes a long time (~60 seconds) for it to timeout. This is for a status page so I want to fail relatively quickly.

I tried to set socket.SendTimeout and socket.RecieveTimeout to 5000ms (5 seconds) but that appears to have no effect.

You might need a workaround. See this similar question: stackoverflow.com/questions/1062035/… — Vlad
– Vlad, Commented Nov 4, 2011 at 22:18

Steve Evans · Accepted Answer · 2011-11-04 22:35:53Z

1

I ended up going with code similar to this to maintain simplicity:

Socket socket = new Socket(AddressFamily.InterNetwork,
                    SocketType.Stream,
                    ProtocolType.Tcp);

IAsyncResult result = socket.BeginConnect(telco.Address, telco.Port, null, null);

bool connectionSuccess = result.AsyncWaitHandle.WaitOne(5000, true);

answered Nov 4, 2011 at 22:35

Steve Evans

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2 Comments

Daniel Mošmondor Over a year ago

Don't run away from threads, as you'll soon or later bump into it since you are doing stuff asynchronously.

Steve Evans Over a year ago

This is for a status page, it checks a few TCP ports to see if they're alive and doesn't ever do anything with them. I think in this scenario running away from threads is the right thing to do.

Community · Accepted Answer · 2017-05-23 12:11:31Z

0

think you're looking for socket.ReceiveTimeout();

or use beginConnect() and use a sync tool such AutoResetEvent to catch the time out.

see this post: How to configure socket connect timeout

edited May 23, 2017 at 12:11

CommunityBot

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answered Nov 4, 2011 at 22:16

MandoMando

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1 Comment

Steve Evans Over a year ago

I had already tried that. I added that to my original question as well. Thanks.

Daniel Mošmondor · Accepted Answer · 2011-11-04 22:30:16Z

To fine control your timeout, do this:

fire up one thread with the code above
after thread is fired and socket connection is attempted, do what you need (i.e. something you have a little time for, at least Application.DoEvents()
Thread.Sleep() for desired timeout interval. Or use some other method to make the time pass
check if the connection is open from your main thread. You can do this by observing some state variable that you'll set after successful connection is made.
if so, use the connection. If not, use Socket.Close() on your waiting socket to break the connection attempt.

Yes, you'll get the exception in the thread that tries to connect, but you can safely gobble it and assume that everything is OK.

http://msdn.microsoft.com/en-us/library/wahsac9k(v=VS.80).aspx Socket.Close()

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