Closing Sockets

Question

Hi all,
Im having a big problem with the closing of sockets.
I have a simple program which handles the sending / receiving and monitoring of HTTP traffic.
My program has a 'sender' part which opens a socket, writes a request (using the socket output stream), reads the response (using the socket input stream, until read() == -1 ) and then closes the streams and socket.
The 'receiver' part simply receives socket connections, reads the content (until read() == -1), writes a response, and then closes the streams and socket.
The monitor part is a simple 'tunnel'. For each received socket connection, a connection is made to a server.
Two threads then operate like this:
T1) While read from client != -1, write to server
T2) While read from server != -1, write to client
Seems simple enough, and sort of works.
The problem I have is cleanly closing all sockets without screwing up either the tunnel or a client.
I try not to close the streams / sockets at the 'logical' times, but for some reason any combination I try results in Socket Closed exceptions during a read in either the tunnel or the client.
There is a fair amount of code - so I dont expect anyone to wade thru it to find the problem, but Im just wondering if anyone has:
1) Had similar problems and found a solution
2) Can point me in the direction for more details on the mechanics and implications of closing socket streams
The java docs seem very sketchy on this subject!!
Thanks for your help!

Answer 1

Thanks for the response (2 dukes for the fast reply - plenty more available on this one though!)....
Does this mean that there is no 'clean' way to accomplish the transfer task?
I think both examples will work, but I have a couple of issues:
This exception is quite normal and indicates that another thread abruptly forced your socket closed or you tried to read or write after closing it yourself. You must catch it.The problem I have with this is that under these circumstances, it is a 'SocketException' which is thrown. The API says that this is thrown if 'there is an error in the underlying protocol, such as a TCP error'. So to be sure I was dealing with the right problem, I'd have to start parsing the exception text looking for "Socket Closed".
Im keener on option 2:
providing signalling between your threads Sounds like this is what I need.... Again there is a catch though.
See, the thread handling the client will be in a blocking read (it will have read everything from the client, and written it to the server. However, as the client socket isn't closed yet, it doesn't know its time to stop). So, Im back to using exceptions again (Im assuming I'd have to do an interrupt?).
I thought I could get round this on the client side by closing the output stream after writing everything (would signify to the reader thread that all is done).
This, however, just results in the socket getting closed (my ignorance of the underlying mechanics of sockets showing through here...).
Further, I want my 'monitor' to work with all request / response based systems - so I cant write a termination sequence on the client side to indicate end of input.
So - Im really stuck with using exceptions as flags then??