Hi,

I have implemented a simple java application (J2SE 1.4.2) in which contains a server and a client.

The server side has a ServerSocket to listen to the client messages and the client side has a for loop to create many socket to a specific port.

When I run the client, the following stack trace was printed after 4 or 5 sockets are created successfully.

java.net.ConnectException: Connection refused
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:305)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:171)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:158)
at java.net.Socket.connect(Socket.java:426)
at java.net.Socket.connect(Socket.java:376)
at java.net.Socket.<init>(Socket.java:291)
at java.net.Socket.<init>(Socket.java:119)
at Client.main(Client.java:12)

I have tested this on both RedHat linux 7.2 and RHEL 3.0 AS and both fail. However I run on Windows XP, it runs without any error.

I have increased the ServerSocket backlog parameter on the server side to a bigger number (default is 50) but it makes no difference. Besides, I have modified /usr/include/linux/socket.h in which the constant SOMAXCONN is changed from 128 to 1024 and it doesn't help as well.

I even tested a similar program of Client Socket in C++ to connect to port 3306, but the exception "Could not bind to port." was caught after 5 or 6 sockets are created. So I am quite sure it's sth wrong with the OS (RedHat Linux).

It seems to be there's some controls or limitations in RedHat Linux which causes the program to throw exception when the clients connect faster than the server can accept.

Any help is appreciated.

i dont think this have anything to do with network, maybe some missing lib in linux that you have in windows.

No, it must be limitation with the Linux 'coz the same program works fine in Windows. I posted a query in Java forum and somebody told me it maybe limited by backlog which is OS dependent, but I have no idea which configuration should be modified to increase the backlog under Linux. (I tried using the method in Java to modify the backlog but no help)

Does somebody has idea to this problem?

yeah, I believe it have something to do with some missing librarie and stuff, thats the point, what librarie, what stuff, but strange is not your question, is where you ask it. Maybe in the Programming Subforum you would get better result...


regards
[ ]'s

Somehow this problem is not program dependant. I even run a simple C++ socket program in Linux but similar result is returned. What I wonder is if there's some configurations in Linux can be modfiied to increase the backlog to a reasonable value.