[Help-smalltalk] Proxy learning exercise

[Stephen]

Hi All,

As a learning exercise I thought I would extend the Wiki Chatserver 
(http://sblinn.jottit.com/GNU_Smalltalk_SimpleEcho_TCP_Server) to create 
a simple forwarding proxy server.

I'm hoping someone can give me a hand...

Simply extending the example of the chat server could result in 
something like the code below...

run
  | source |
  [
    ss waitForConnection.
    source := (ss accept).
    [self handleSocket: source] fork
  ] repeat
!!

"Instance method to handle each connection"
!SimpleProxyServer methodsFor: 'handling'!

handleSocket: source
  | msg dest |
  dest := (TCP.Socket remote: amailserver port: 25).
  [
    "handle source data"
    msg := (source nextHunk).
    msg displayOn: dest.
    dest flush.
    "handle dest data"
    msg := (dest nextHunk).
    msg displayOn: source.
    source flush.
  ] repeat
!!

-----------------------

But the code above wouldn't work since it blocks on input from source 
and there may be data in the dest Stream. So I modified handleSocket to 
look like this...

run
  | source |
  [
    ss waitForConnection.
    source := (ss accept).
    [self handleSocket: source] fork
  ] repeat
!!

"Instance method to handle each connection"
!SimpleProxyServer methodsFor: 'handling'!

handleSocket: source
  | msg dest |
  dest := (TCP.Socket remote: amailserver port: 25).
  [
    "handle source data"
    (source available) ifTrue: [
            msg := (source nextHunk).
            msg displayOn: dest.
            dest flush ].
    "handle dest data"
    (dest available) ifTrue: [
                msg := (dest nextHunk).
                msg displayOn: source.
                source flush ].
  ] repeat
!!
 -----------------------

And this is where I'd like a hand. The code above works as a relay but 
isn't suitable because:
 1. It doesn't close the client (source) socket when the server (dest) 
socket closes.
 2. The loop is CPU intensive

I would like to know how to block until _either_ the "source" socket, 
or, the "dest" socket has some data.
Also, if either of the source or dest sockets is closed then the thread 
should terminate and close any sockets owned by the thread.

Thanks
Stephen