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ServerSocket

Posted on 2001-07-19
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Last Modified: 2012-06-27
Hiya,

I created the 'standard' echo-server using the ServerSocket. Each new connection is handled in its own thread. it all works fine with a few clients.

I then wrote a small client that creates heaps of threads each trying to connect to the echo-server.. this gives me unpredictable errors.. If i startup n-clients (in n-threads) anywhere from 0-n threads can't connect to the echo-server and come back with a :

java.net.ConnectException: Connection refused: no further information
        at java.net.PlainSocketImpl.socketConnect(Native Method)
        at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:312)
        at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:125)
        at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:112)
        at java.net.Socket.<init>(Socket.java:273)
        at java.net.Socket.<init>(Socket.java:100)
        at mytestpackage.testConnectionThread.run(testConnectionThread.java:38)

from the
Socket aSocket = new Socket("127.0.0.1",portNumber);
statement..

I'm running JDK1.3 on NT4.0 SP6 but hope it is not an OS problem..

Any Idea's "?

best regards,
tom
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Question by:tomschuring1
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9 Comments
 
LVL 92

Expert Comment

by:objects
ID: 6301084
I think there's a os limit to the number of open sockets.
WHat was the error (if any) on the server side?
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LVL 92

Expert Comment

by:objects
ID: 6301093
It could also possibly be running out of threads??
How many connections are we talking about?
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Expert Comment

by:objects
ID: 6301095
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Expert Comment

by:jerrycao
ID: 6301626
it is better to paste ur source code here...
if u do not mind.
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LVL 2

Expert Comment

by:userquin
ID: 6301638
Hi:

In server side you create a ServerSocket. If you use ServerSocket(int port) constructor it creates a queue for incoming requests with a lenght of 50. If you exceed 50 (queue is full) connections it throws a ConnectionException exception (refused, what you catch).

You can prefix queue length using ServerSocket(int port, int backlog) constructor. I do not know if there is a OS restriction for this.

Bye.

J.
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Expert Comment

by:swapsthegreat
ID: 6302232
i think the queue limit is 25 connections
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Author Comment

by:tomschuring1
ID: 6306713
the minimum number of connections that I can get it to happen with is 100

I did do do a mServerSocket = new ServerSocket(port,1000);

just to make sure it is not the QueueSize that blows me up.

There is no error on the server side at all.

I have just moved the server to a windowsNT Server (I am running workstation) and it started to accept all connections. mmmmm seems to work properly now. what do i do with the points ? Howabaout I'll give them to someone who can explain why it doesn't work on workstation ?
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LVL 92

Accepted Solution

by:
objects earned 400 total points
ID: 6306750
At a guess it has a smaller limit on open sockets.
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LVL 92

Expert Comment

by:objects
ID: 6307190
Sorry I couldn't give a more definitive answer.
Thanks for the points :)
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