Now today I was testing Server and Client code on different machine. Both were on same Wi-fi network.
I created clients using below code and got this exception for many threads :
java.net.ConnectException: Connection timed out: no further information
at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
at sun.nio.ch.SocketChannelImpl.finishConnect(Unknown Source)
at SocketTest.connect(Client.java:188)
at SocketTest.run(Client.java:73)
at java.lang.Thread.run(Unknown Source)
the line 73 is connect(key)
and line 188 is if(!(channel.finishConnect()))
So the client thread was unable to connect because no reply came from server ? Right ?
Question)When I run both Server and Client on same machine localhost this exception does not arise. What may be the reasons ? (network problem ?).
Also I also use Backlog queue parameter in public void bind(SocketAddress endpoint,int backlog) as 2000. While exact size is unknown(around 200 ?) but I am using a large value so that maximum value will be used.(Right ? or Java will make a queue ?).
Can this be a reason : The Server puts the request in backlog queue and till it gets time to serve it, the timeout may have happened at Client ?
Client :
public class Client {
public static void main(String[] args) {
int n=100;
SocketTest [] st= new SocketTest[n];
for(int i=0;i<n;i++)
st[i]= new SocketTest("hi");
for(int i=0;i<n;i++)
{
if(i%50 == 0)
try{
Thread.sleep(5000);
}
catch(InterruptedException ie)
{
System.out.println(""+ie);
}
new Thread(st[i]).start();
}
}
}
class SocketTest implements Runnable {
private String message = "";
ByteBuffer readBuffer = ByteBuffer.allocate(1000);
private Selector selector;
private int i;
public static AtomicInteger cnt= new AtomicInteger(0);
public SocketTest(String message){
this.message = message;
}
@Override
public void run() {
SocketChannel channel;
try {
selector = Selector.open();
channel = SocketChannel.open();
channel.configureBlocking(false);
channel.register(selector, SelectionKey.OP_CONNECT);
channel.connect(new InetSocketAddress("192.168.1.10", 8511));
while (!Thread.currentThread().isInterrupted()){
selector.select();
Iterator<SelectionKey> keys = selector.selectedKeys().iterator();
while (keys.hasNext()){
SelectionKey key = keys.next();
keys.remove();
if (!key.isValid()) continue;
if (key.isConnectable()){
connect(key);
System.out.println("I am connected to the server");
}
if (key.isWritable()){
write(key);
}
if (key.isReadable()){
read(key);
}
}
}
}
catch(ClosedByInterruptException e)
{
// let go of thread
}
catch(CancelledKeyException e){
e.printStackTrace();
}
catch (IOException e1) {
System.out.println("IOE Occured|maybe Server died");
e1.printStackTrace();
} finally {
close();
}
}
private void close(){
try {
if(selector!=null)
selector.close();
}
catch(Exception e)
{
e.printStackTrace();
}
}
private void read (SelectionKey key) throws IOException {
SocketChannel channel = (SocketChannel) key.channel();
readBuffer.clear();
int length;
try{
length = channel.read(readBuffer);
} catch (IOException e){
System.out.println("Reading problem, closing connection for : "+channel.getLocalAddress());
key.cancel();
channel.close();
return;
}
if (length == -1){
System.out.println("Nothing was read from server");
channel.close();
key.cancel();
return;
}
readBuffer.flip();
byte[] buff = new byte[1024];
readBuffer.get(buff, 0, length);
//length=buff.length;
String fromserver = new String(buff,0,length,"UTF-8");
length = fromserver.length();
System.out.println("Server said: "+fromserver);
key.interestOps(SelectionKey.OP_WRITE);
}
private void write(SelectionKey key) throws IOException {
SocketChannel channel = (SocketChannel) key.channel();
i++;
message = "location now "+i;
if(i==2)
{
cnt.addAndGet(1);
System.out.println("****"+cnt.get()+"****");
}
try{
Thread.sleep(5000);
}
catch(InterruptedException ie)
{
System.out.println(""+ie);
//Thread.currentThread().interrupt();
}
//assuming all goes in one shot
channel.write(ByteBuffer.wrap(message.getBytes()));
key.interestOps(SelectionKey.OP_READ/*|SelectionKey.OP_WRITE*/);
}
private void connect(SelectionKey key){
SocketChannel channel= (SocketChannel) key.channel();
try
{
if(!(channel.finishConnect())){
//System.out.println("* Here *");
return;
}
}
catch(ConnectException e){
System.out.println("Conect Exception");
e.printStackTrace();
try{channel.close();}
catch(IOException ie){ie.printStackTrace();key.cancel();return;}
return;
}
catch(IOException e)
{
System.out.println("BP 1"+e);
e.printStackTrace();
try{channel.close();}
catch(IOException ie){ie.printStackTrace();key.cancel();return;}
return;
}
//channel.configureBlocking(false);
//channel.register(selector, SelectionKey.OP_WRITE);
key.interestOps(SelectionKey.OP_WRITE);
}
}
The connect timed out because the server didn't reply.
When I run both Server and Client on same machine localhost this exception does not arise. What may be the reasons ? (network problem ?).
Why should it arise? The server is there, the client is there, no network problems in between. The question doesn't make sense.
Also I also use Backlog queue parameter in public void bind(SocketAddress endpoint,int backlog) as 2000. While exact size is unknown(around 200 ?) but I am using a large value so that maximum value will be used. Right?
Right.
or Java will make a queue?
I don't know what this means. Java doesn't do anything with the backlog parameter. It goes straight to TCP.
Can this be a reason: The Server puts the request in backlog queue and till it gets time to serve it, the timeout may have happened at Client ?
No. Only completed connections go on the backlog queue.