The problem turns out to be in 

Socket>>#connectTo: hostAddress port: port waitForConnectionFor: timeout 

"Initiate a connection to the given port at the given host 

address. Waits until the connection is established or time outs."

self connectNonBlockingTo: hostAddress port: port.

self

waitForConnectionFor: timeout

ifTimedOut: [ConnectionTimedOut signal: 'Cannot connect to '

, (NetNameResolver stringFromAddress: hostAddress) , ':' , port asString]

When a socket is created three external semaphores are registered in the ExternalSemaphoreTable. If a connection times out the exception is thrown but the Socket still has his resources attached. 

So e.g. in 

SocketStream class>>#openConnectionToHost: hostIP port: portNumber timeout: timeout

| socket |

socket := Socket new.

socket connectTo: hostIP port: portNumber waitForConnectionFor: timeout.

^self on: socket

it holds locally a socket (with semaphores registered) but on exception time the reference to the socket gets lost and the semaphores stay registered. The only way to unregister is on finalization time but I think it should work better. So I would add a destroy before the exception is raised.

I opened a ticket at https://pharo.fogbugz.com/f/cases/11797 but I'm not sure how I am supposed to provide fixes made against a pharo2.0 image. Probably I should fix this againt 3.0 but then I'm still a 2.0 user :) 

Norbert