How to check if a server is listening without exception handling

I'm working on two apps that connect to eachother using TCP. At one point, one of them is trying to connect using a TcpClient, but the other app is not guaranteed to have started listening yet (using TcpListener).

My first attempt was this:

TcpClient c = null;
while (true)
{
    try
    {
        c = new TcpClient();
        c.NoDelay = true;
        c.Connect( ip, port );
        break;
    }
    catch (SocketException ex)
    {
        Console.WriteLine(string.Format("Could not connect to {0}:{1}, retrying...", ip, port));
        Thread.Sleep( 500 );
    }
}

However, the problem with this is that it relies on exception handling which is a bit of a nuisance for me, because I have VS set up to catch any thrown exceptions ("Debug -> Exceptions..." menu). So every time it tries to connect, it breaks into VS and I have to press continue.

The exception I get is:

No connection could be made because the target machine actively refused it 127.0.0.1:50000

I would imagine that there would be a way to check if a server is listening on a specific port without actually trying to connect to it. I understand that just checking wouldn't be enough anyway - the server could go down between the check and the connect attempt, but it would still be much better for me while I'm developing it.

Or something like this:

TcpClient tcpClient = new TcpClient();
while ( !tcpClient.TryConnect(....) )
{ Thread.Sleep(1000); }

Analogous to this:

if (bool.TryParse( "false" ))
{ ... }

I also tried using async methods (Begin/End Connect) and setting the timeout for the ManualResetEvent manually, but that didn't work either. I've开发者_StackOverflow中文版 scoured the internets but I haven't been able to find a solution to this problem, which is why I'm finally posting here :)

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The problem being that VS is breaking on the Exception? You you can always have VS ignore a specific family of Exceptions.

In VS, in the Debug Menu, choose "Exceptions..." and in the dialog presented you can control this.

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I was going to suggest not catching an exception, so before I suggested that I test it myself, and if you set it to throw all exceptions even if you don't throw an exception its all exceptions are still being thrown. I will have to agree with Shiv Kumar, either adjust your settings while you debug your application, or accept the limitations of what you are doing.

The reason bool.TryParse works is it verifys each and every character, similarly to how Int32.TryParse makes sure that each character in the string is 0-9 or any other valid numerical symbol.

You could of course write your own networking class and not throw an exception when the connection fails.

TryParse will not throw an exception, you must catch any exception that is thrown if you use bool.Parse by try{}catch{} otherwise if you attempt to parse something that is not a boolean value it will throw an unhandled exception. TryParse was added later in the history of .NET, Parse is more of the classic method, allowing the programmer to handle all unexpected input and to validate input before trying to parse the data.

I should add that TryParse will return false if its unable to parse the value at both the method's result is false and the out variable I do believe is false.This is at least the case with Int32

http://msdn.microsoft.com/en-us/library/system.boolean.tryparse.aspx

I guess the point of pointing out how TryParse and Parse works is that they are entirely different beasts compare to TcpClient. I suppose I should clarify that the basic validation process is similar, except one throws an exception and the other one doesn't and of course one returns what was actually parsed.