Not many Java programmers knows that socket connections are treated similar files together with they role file descriptor, which is a express resource. Different operating organisation has unlike limits on unwrap of file handles they tin manage. One of the mutual argue of java.net.SocketException: Too many files open inward Tomcat, Weblogic or any Java application server is, likewise many clients connecting together with disconnecting oft at rattling curt bridge of time. Since Socket connexion internally role TCP protocol, which says that a socket tin stay inward TIME_WAIT Blue Planet for or together with therefore time, fifty-fifty afterwards they are closed. One of the argue to continue shut socket inward TIME_WAIT Blue Planet is to ensure that delayed packets reached to the corresponding socket. Different operating organisation has unlike default fourth dimension to continue sockets inward TIME_WAIT state, inward Linux it's lx seconds, piece inward Windows is iv minutes. Remember longer the timeout, longer your shut socket volition continue file handle, which growth chances of java.net.SocketException: Too many files opened upwardly exception.
This also means, if y'all are running Tomcat, Weblogic, Websphere or whatever other web server inward windows machine, y'all are to a greater extent than prone to this fault than Linux based systems e.g. Solaris or Ubuntu.
By the way this fault is same every bit java.io.IOException: Too many files opened upwardly exception, which is throw past times code from IO bundle if y'all attempt to opened upwardly a novel FileInputStream or whatever current pointing to file resource.
This also means, if y'all are running Tomcat, Weblogic, Websphere or whatever other web server inward windows machine, y'all are to a greater extent than prone to this fault than Linux based systems e.g. Solaris or Ubuntu.
By the way this fault is same every bit java.io.IOException: Too many files opened upwardly exception, which is throw past times code from IO bundle if y'all attempt to opened upwardly a novel FileInputStream or whatever current pointing to file resource.
How to solve java.net.SocketException: Too many files open
Now, nosotros know that this fault is coming because clients are connecting together with disconnecting frequently. If that's seems odd to your application, y'all tin detect the culprit customer together with prohibit them from reconnecting from making a connection, only if that is something, your application may await together with y'all wish to receive got it on your side, y'all accept ii options : 1) Increase unwrap of opened upwardly file handles or file descriptors per process.
2) Reduce timeout for TIME_WAIT Blue Planet inward your operating system
In UNIX based operating organisation e.g. Ubuntu or Solaris, y'all tin role ascendance ulimit -a to detect out how many opened upwardly file handles per procedure is allowed.
$ ulimit -a
core file size (blocks, -c) unlimited
data seg size (kbytes, -d) unlimited
file size (blocks, -f) unlimited
open files (-n) 256
pipe size (512 bytes, -p) 10
stack size (kbytes, -s) 8192
cpu time (seconds, -t) unlimited
max user processes (-u) 2048
virtual memory (kbytes, -v) unlimited
You tin encounter that, opened upwardly files (-n) 256, which agency alone 256 opened upwardly file handles per procedure is allowed. If your Java program, retrieve Tomcat, weblogic or whatever other application server are Java programs together with they run on JVM, exceeds this limit, it volition throw java.net.SocketException: Too many files opened upwardly error.
You tin alter this bound past times using ulimit -n
Another of import matter to verify is that, your procedure is non leaking file descriptors or handles, good that's a dull matter to detect out, only y'all tin role lsof ascendance to banking concern check how many opened upwardly file handles is owned past times a item procedure in UNIX or Linux. You tin run lsof ascendance past times providing PID of your process, which y'all tin teach it from ps command.
Similarly, y'all tin alter TIME_WAIT timeout, only create amongst consultation of UNIX support, every bit a actually depression fourth dimension means, y'all mightiness missy delayed packets. In UNIX based systems, y'all ca n encounter electrical current configuration inward /proc/sys/net/ipv4/tcp_fin_timeout file. In Windows based system, y'all tin encounter this information inward windows registry. You tin alter the TCP TIME_WAIT timeout inward Windows past times next below steps :
1) Open Windows Registry Editor, past times typing regedit inward run ascendance window
2) Find the fundamental HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\tcpip\Parameters
3) Add a novel fundamental value yoke TcpTimedWaitDelay asa decimal together with laid the desired timeout inward seconds (60-240)
4) Restart your windows machine.
Remember, y'all mightiness non accept permission to edit windows registry, together with if y'all are non comfortable, amend non to create it. Instead enquire Windows Network back upwardly team, if y'all accept any, to create that for you. Bottom occupation to fix java.net.SocketException: Too many files open, is that either increasing unwrap of opened upwardly file handles or reducing TCP TIME_WAIT timeout. java.net.SocketException: Too many files open upshot is also mutual among FIX Engines, where customer role TCP/IP protocol to connect amongst brokers FIX servers. Since FIX engines needs right value of incoming together with outgoing sequence unwrap to establish FIX session, and if customer tries to connect amongst a smaller sequence unwrap than expected at brokers end, it disconnects the session immediately. If customer is good behind, together with continue retrying past times increasing sequence unwrap past times 1, it tin crusade java.net.SocketException: Too many files open at brokers end. To avoid this, let's FIX engine continue rails of it's sequence number, when it restart. In short, "java.net.SocketException: Too many files open" can move seen whatever Java Server application e.g. Tomcat, Weblogic, WebSphere etc, amongst customer connecting together with disconnecting frequently.
Further Learning
Java Memory Management
Understanding the Java Virtual Machine: Memory Management
Understanding together with Solving Java Memory Problems