java.net.SocketException: Too many open files

[Ramasubramaniam Rathinasubbu]

2010-08-29 00:57:26,263 ERROR [org.apache.tomcat.util.net.JIoEndpoint] Socket accept failed
java.net.SocketException: Too many open files
at java.net.PlainSocketImpl.socketAccept(Native Method)
at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:390)
at java.net.ServerSocket.implAccept(ServerSocket.java:453)
at java.net.ServerSocket.accept(ServerSocket.java:421)
at org.apache.tomcat.util.net.DefaultServerSocketFactory.acceptSocket(DefaultServerSocketFactory.java:61)
at org.apache.tomcat.util.net.JIoEndpoint$Acceptor.run(JIoEndpoint.java:310)
at java.lang.Thread.run(Thread.java:619)


OS : Linux
Application server : Jboss application server
many times i am getting this error.
could you give the reason?....