Not many Java programmers knows that socket connections are treated like files and they use file descriptor, which is a limited resource. Different operating system has different limits on number of file handles they can manage. One of the common reason of java.net.SocketException: Too many files open in Tomcat, Weblogic or any Java application server is, too many clients connecting and disconnecting frequently at very short span of time. Since Socket connection internally use TCP protocol, which says that a socket can remain in TIME_WAIT state for some time, even after they are closed. One of the reason to keep closed socket in TIME_WAIT state is to ensure that delayed packets reached to the corresponding socket. Different operating system has different default time to keep sockets in TIME_WAIT state, in Linux it's 60 seconds, while in Windows is 4 minutes. Remember longer the timeout, longer your closed socket will keep file handle, which increase chances of java.net.SocketException: Too many files open exception. This also means, if you are running Tomcat, Weblogic, Websphere or any other web server in windows machine, you are more prone to this error than Linux based systems e.g. Solaris or Ubuntu. By the way this error is same as java.io.IOException: Too many files open exception, which is throw by code from IO package if you try to open a new FileInputStream or any stream pointing to file resource.
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