How to get a free port ?

How to get a free port ?

• Michiel0099

  Ok, thanks a lot, I will try this. But I am curious where did you get this info from I mean, this point is not mentionned in the documentation (even the author of the book Advance .Net Remoting did ignore this element)
  
  Also I have an additional question, how can I know on which port the TcpChannel has been instanciated
  
  Joannes
  
  

• alexgr

  What I'm missing from this discussion is if you create a server channel and cause it to pick a port for you, how does the client know how to construct the Activator.GetObject(...) URL parameter which usually contains the port the server object is using in its channel transport. E.g. client URL: "tcp://localhost:7777/RemoteObjURI.rem"

  Or do you do the same in client Activator as the server channel instanciation, i.e. use the following URL: "tcp://localhost:0/RemoteObjURI.rem" or "tcp://localhost/RemoteObjURI.rem"

  Thanks in advance.

  
  

• ncj

  I don't believe Remoting can do this for you, you need an out of band mechanism to let the client know what the port is.
  
  

• JulesW

  Joannes Vermorel wrote:

  Ok, thanks a lot, I will try this. But I am curious where did you get this info from I mean, this point is not mentionned in the documentation

  Following the documentation link you provided, the first sentence in the Remarks section says "To request that the remoting system choose an open port on your behalf, specify port "0" (zero). "
  
  

  Also I have an additional question, how can I know on which port the TcpChannel has been instanciated

  For TcpChannel I think you'd have to use ChannelData to retrieve the channel URI and parse that.
  
  If you aren't using remoting then a TcpListener might be a better class to use.
  http://msdn2.microsoft.com/library/c4zw1w3a(en-us,vs.80).aspx  With TcpListener, you can still use zero to let the system pick your port number and then use the LocalEndpoint property to find out what port number you got.
  

• mydarlingdarla

  Simply pass zero to the constructor of the TcpChannel. The system will then worry about finding a free port. This works in .NET 1.0/1.1 as well as .NET 2.0.
  
  

• tombraider

  what you describe is a discovery mechanism. remoting doesn't and will likely never have support for discovery.

  WCF doesn't have support for discovery either in the current release, though there is a sample that allows you to use it:

  http://wcf.netfx3.com/files/folders/protocol_channels/entry7909.aspx

  
  
  

• Louis315

  Thank you ranamauro for your response. I do believe you are correct. However, just for grins I'm going to test my theory.

  So the CLR remoting channel mechanism can't simply lookup an endpoint by the URI, the "foo.rem" part of the URL, amongst all the registered endpoints on the server designated by the URL It seems to me that unique registered URIs could be enforced for those server channel requests that pick a port on the caller's behalf by having the registration process return an error for a duplicate endpoint of this kind. Is there anybody out there that is definitive about the answer to my question

  
  
• How to get a free port ?