Re: Socket problems
- From: "JS" <james.sarjeant90@xxxxxxxxxxxx>
- Date: Sat, 19 Nov 2005 15:17:42 GMT
Hi Knute,
Would it be possible to email that code you mentioned to me at
james.sarjeant90@xxxxxxxxxxxx
Hi Oliver, we did try using a while(true) loop and it seemed to have less
effect than the other method
My group has tried loads of things and we really are getting stuck for
ideas. Any help is appreciated.
Thanks everyone and any more ideas are always welcome
JS
"Knute Johnson" <nospam@xxxxxxxxxxxxxxxxx> wrote in message
news:VTpff.16199$lM1.3178@xxxxxxxxxxx
> JS wrote:
> > Hi everyone. I'm trying to write a 20 client chat server which is not
web
> > based (the only reason I say that is because all the examples I have
found
> > so far are applets, JSP etc)
> > In the client side I'm trying to listen for input from the user and for
> > messages from the server at the same time. Well almost, there is a
SoTimeout
> > of 50milliseconds which swaps between listening from the System.in and
the
> > server.
> >
> > A similar story on the server side but this calls methods for listening
for
> > new clients connecting and messages from the existing clients. The
server
> > has this code:
> >
> > public void receive()
> > {
> > System.out.println("Waiting for new clients");
> > try
> > {
> > socket = serverSocket.accept();
> > socket.setSoTimeout(50);
> > BufferedReader inFromClient = new BufferedReader(new
> > InputStreamReader(socket.getInputStream()));
> > String clientSentence = inFromClient.readLine();
> > System.out.println("someone said "+clientSentence);
> > process(clientSentence, socket);
> > }
> > catch(IOException e)
> > {
> > System.out.println(e);
> > System.out.println("A new client could not be found");
> > listenFromClients();
> > }
> > listenFromClients();
> > }
> >
> > public void listenFromClients()
> > {
> > System.out.println("Waiting for a known client to speak");
> > for(int i = 0; i < clients.size(); i++)
> > {
> > Tuple t = (Tuple)clients.get(i);
> > socket = t.getSocket();
> > try
> > {
> > socket.setSoTimeout(50);
> > BufferedReader in = new BufferedReader(new
> > InputStreamReader(socket.getInputStream()));
> > String clientSentence = in.readLine();
> > System.out.println(t.getName()+ " said
"+clientSentence);
> > process(clientSentence, socket);
> > }
> > catch(IOException e)
> > {
> > System.out.println(e);
> > System.out.println("Known client "+i+" timed out");
> > continue;
> > }
> > }
> > receive();
> > }
> >
> > and the client has this:
> >
> > public void start()
> > {
> > String first = connect();
> > if(first != null)
> > {
> > send(first);
> > }
> > while(true)
> > {
> > receive();
> > getClientInput();
> > }
> >
> > }
> >
> > public String connect()
> > {
> > try
> > {
> > String toServer = InetAddress.getLocalHost().getHostName();
> > return ("connect: "+toServer+" "+name+"\n");
> > }
> > catch(IOException e)
> > {
> > System.out.println(e);
> > System.out.println("The host name of your computer could not
be
> > found");
> > System.out.println("The system will now exit");
> > System.exit(3);
> > }
> > return null;
> > }
> >
> > public void send(String message)
> > {
> > try
> > {
> > DataOutputStream outToServer = new
> > DataOutputStream(socket.getOutputStream());
> > outToServer.writeBytes(message);
> > receive();
> > }
> > catch(IOException e)
> > {
> > System.out.println(e);
> > System.out.println("The message could not be sent");
> > }
> > }
> >
> > public void receive()
> > {
> > try
> > {
> > BufferedReader inFromServer = new BufferedReader(new
> > InputStreamReader(socket.getInputStream()));
> > String sentence = inFromServer.readLine();
> > process(sentence);
> > }
> > catch(IOException e)
> > {
> > System.out.println(e);
> > System.out.println("The message could not be received
hello");
> > //getClientInput();
> > }
> >
> > }
> >
> > public void getClientInput()
> > {
> > try
> > {
> > BufferedReader inFromClient = new BufferedReader(new
> > InputStreamReader(System.in));
> > System.out.println("Enter some text....");
> > String in = inFromClient.readLine();
> > send("message: "+name+": "+in);
> > }
> > catch(IOException e)
> > {
> > System.out.println(e);
> > System.out.println("That message could not be read from
you");
> > //receive();
> > }
> > }
> >
> > The socket keeps timing out and the errors are caught but neither class
> > seems to carry on listening with the other method. I would use threads
but
> > Sockets and networks are new to me let alone threads as well, although
it
> > might be possible with some collaboration.
> > There are a lot of System.out.println() statments here purely so we
could
> > see what was happening. Now in theory the server should print out a new
line
> > each time it swaps methods but it doesnt.
> > Any help is greatly appreciated and if you need any further details then
> > feel free to ask.
> > Thanks a lot everyone
> > JS
> >
>
> JS:
>
> You are going to need to use threads. They really aren't as complicated
> as they seem if you keep your logic simple. With what you have your
> sockets will time out and close. No communications will happen then.
>
> The server end needs to do two basic things, handle incoming connections
> and create threaded tasks that will send data between each other and to
> and from the clients.
>
> This is the basic logic for a simple connection handler:
>
> ServerSocket ss = new ServerSocket(SOMEPORT);
> while (true) {
> Socket s = ss.accept(); // wait for connection
> // create a new communicator task and pass it the socket
> CommTask ct = new CommTask(s);
> // add reference to the task to a vector
> commTaskVector.add(ct);
> }
>
> The communicator task then needs to receive data from its client and
> pass it to the other communicator tasks and receive data from the other
> communcator tasks and pass it to its client.
>
> class CommTask implements Runnable {
> OutputStream os;
> InputStream is;
>
> public CommTask(Socket s) {
> is = s.getInputStream();
> os = s.getOutputStream();
>
> new Thread(this).start(); // start thread - it executes run()
> }
>
> public void run() {
> // read from input stream
> // iterate through commTaskVector and write data to
> // other tasks via their write method
> }
>
> public void write(bye[] buf) {
> // write data from other tasks to output stream
> }
>
> This is just an outline. You will need to handle the IOExceptions,
> timeouts, and cleanup when clients leave. The write methods will have
> to be synchronized as will access to the Vector that holds the list of
> communicator tasks.
>
> A chat server is really a pretty compilicated thing when you get right
> down to it. I have a simple UDP transceiver that I wrote to communicate
> between two points that I would be happy to give you the source code
> for. It might be fun to play with and would be a start to see how
> multithreaded code works.
>
> --
>
> Knute Johnson
> email s/nospam/knute/
.
- References:
- Socket problems
- From: JS
- Re: Socket problems
- From: Knute Johnson
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