Networking

if anyone can give me a strategy (I don t need it spelled out to me just general "I used this

function type help) I d really appreciate it.

Answer 1: I ve found the only way to unblock a (Socket) read blocking thread is to close() the

socket from another thread. That ll throw an IOException in the read() call.

Michiel

Answer 2: Another method that seems to work is to set a socket timeout to something

moderately short (like 10 seconds). The blocked read will throw an exception when the

timeout occurs. Then the thread can inspect the state of a variable (set by another thread

calling an appropriate method) to see if it should terminate.

This approach also makes it trivial to implement a longer inactivity timeout if desired and gives

the network thread an opportunity to do some maintenance work if it wants.

Peter

Q: I get the impression that only read operations from a Sockets InputStream throw an

Exception if the opposite Socket has closed the socket. Writing to the Socket s outputStream

works fine...

Is there a way to detect if what I write into a Socket s outputstream is actually still being

received by the other side? 

Or will I have to check that I actually get a response via the InputStream, and if not, try to open

a new Socket and resend the request again?

Answer: You can try calling flush() after writing the output, but there s no guarantee that you ll

get an immediate exception. The underlying TCP/IP software may go through timeout and

retry logic before giving up. 

That s probably why you ll usually find out about a broken socket when waiting to read. You

should rewrite client so that it sends a request and waits for a response. If it doesn t get a

response, it should try to make a new connection and do the request/response thing again. 

If it doesn t work the second time, it should give up for the time being. Perhaps it really makes

sense that one has to verify  by hand  that requests go through.

Duane Morse

 Q: ... I imagine, I ll have to cut my file into small datagrams.

I just made a little chat program (client and server) and I would like to add the possibility to

transfer files.

The client and the server are communicating with TCP/IP using a socket.

I imagine, I ll have to cut my file into small datagrams. Is it necessary ? Has someone an idea

or a link to source code of such a function ??

Answer: No. If you were using UDP/IP (DatagramSocket and friends) then it would need to be

split up. The point of TCP is to avoid this need. Simple send the entire file in a stream.

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