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non blocking echo client problem

 
 
jimgardener
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Posts: n/a
 
      07-02-2008
i tried to implement a non blocking echoclient using java.nio
it connects to an echoserver and takes userinput and writes to
server .Then it reads from server and prints the server message

however ,i found that the socketchannel.isConnected() is false in the
while loop where key.readyOps is equal to OP_CONNECT

i am not sure what i am doing wrong..Am a beginner with nio and
networking..can someone help?


here is the code>>>

import java.io.*;
import java.nio.*;
import java.nio.channels.*;
import java.net.*;
import java.util.*;
public class EchoClient {
int port;
ByteBuffer buf=ByteBuffer.allocate(1024);
Selector sel=null;
SocketChannel sc=null;
public EchoClient(int p)throws IOException{
port=p;
initClient();
}
private void initClient()throws IOException{
sel=Selector.open();
sc=SocketChannel.open();
sc.configureBlocking(false);
sc.connect(new
InetSocketAddress(InetAddress.getLocalHost(),this. port));
sc.register(sel, SelectionKey.OP_CONNECT);

while(true){
sel.select();
Set<SelectionKey> selectedkeys=sel.selectedKeys();
Iterator<SelectionKey> it=selectedkeys.iterator();
while(it.hasNext()){
SelectionKey key=it.next();
int readyops=key.readyOps();
if((readyops& SelectionKey.OP_CONNECT)==SelectionKey.OP_CONNECT) {

debug("connected to server:"+sc.isConnected());
sc.register(sel, SelectionKey.OP_READ);
debug("registered for read");
debug("now write to server");
getUserinputAndWrite();
it.remove();
}
else if((readyops& SelectionKey.OP_READ)==SelectionKey.OP_READ){
debug("read from server");
debug("connected to server:"+sc.isConnected());
buf.clear();
int numread=0;
while((numread=sc.read(buf) )!= -1){
debug("server said:"+new String(buf.array(),0,numread));
}
it.remove();
}

}



}

}

private void getUserinputAndWrite()throws IOException{

BufferedReader userin=new BufferedReader(new
InputStreamReader(System.in));
String userinput=null;
debug("enter user input:");
while((userinput=userin.readLine()) !=null){
debug("u entered:"+userinput);
debug("still connected to server:"+sc.isConnected());
byte[] userbits=userinput.getBytes();
buf.clear();
buf.put(userbits);
buf.flip();
sc.write(buf);

if(userinput.equals("bye"))break;
}
}

public static void main(String[] args) {
if (args.length !=1)debug("usage:EchoClient port");
try{
new EchoClient(Integer.parseInt(args[0]));

}catch(IOException e){
e.printStackTrace();
}

}
public static void debug(String msg){
System.out.println(msg);
}

}

this is the output i got>>>java EchoClient 9000
connected to server:false
registered for read
now write to server
enter user input:
hello there
u entered:hello there
still connected to server:false
Exception in thread "main" java.nio.channels.NotYetConnectedException
at sun.nio.ch.SocketChannelImpl.ensureWriteOpen(Unkno wn
Source)
at sun.nio.ch.SocketChannelImpl.write(Unknown Source)
at EchoClient.getUserinputAndWrite(EchoClient.java:69 )
at EchoClient.initClient(EchoClient.java:35)
at EchoClient.<init>(EchoClient.java:13)
at EchoClient.main(EchoClient.java:7
 
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GArlington
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Posts: n/a
 
      07-02-2008
On Jul 2, 10:03 am, jimgardener <(E-Mail Removed)> wrote:
> i tried to implement a non blocking echoclient using java.nio
> it connects to an echoserver and takes userinput and writes to
> server .Then it reads from server and prints the server message
>
> however ,i found that the socketchannel.isConnected() is false in the
> while loop where key.readyOps is equal to OP_CONNECT
>
> i am not sure what i am doing wrong..Am a beginner with nio and
> networking..can someone help?
>
> here is the code>>>
>
> import java.io.*;
> import java.nio.*;
> import java.nio.channels.*;
> import java.net.*;
> import java.util.*;
> public class EchoClient {
> int port;
> ByteBuffer buf=ByteBuffer.allocate(1024);
> Selector sel=null;
> SocketChannel sc=null;
> public EchoClient(int p)throws IOException{
> port=p;
> initClient();
> }
> private void initClient()throws IOException{
> sel=Selector.open();
> sc=SocketChannel.open();
> sc.configureBlocking(false);
> sc.connect(new
> InetSocketAddress(InetAddress.getLocalHost(),this. port));
> sc.register(sel, SelectionKey.OP_CONNECT);

<snap>
You should read docs for NIO SocketChannel.connect() method... You
might find that it returns boolean result and what it means and what
you are meant to do if that result is false...
 
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EJP
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Posts: n/a
 
      07-03-2008
OP_CONNECT means that you must now call finishConnect(). If this returns
true, so will sc.isConnected(). Not before.
 
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