java ssh框架开发的网站,上周末重启下tomcat 6.0 ,代码没有修改和替换过，每天晚上9点左右死掉为什么?

Servlet.service() for servlet default threw exception
java.net.SocketException: Connection reset by peer: socket write error
at java.net.SocketOutputStream.socketWrite0(Native Method)
at java.net.SocketOutputStream.socketWrite(Unknown Source)
at java.net.SocketOutputStream.write(Unknown Source)
at org.apache.coyote.http11.InternalOutputBuffer.realWriteBytes(InternalOutputBuffer.java:760)
at org.apache.tomcat.util.buf.ByteChunk.flushBuffer(ByteChunk.java:439)
at org.apache.tomcat.util.buf.ByteChunk.append(ByteChunk.java:354)
at org.apache.coyote.http11.InternalOutputBuffer$OutputStreamOutputBuffer.doWrite(InternalOutputBuffer.java:784)
at org.apache.coyote.http11.filters.ChunkedOutputFilter.doWrite(ChunkedOutputFilter.java:124)
at org.apache.coyote.http11.InternalOutputBuffer.doWrite(InternalOutputBuffer.java:593)
at org.apache.coyote.Response.doWrite(Response.java:560)
at org.apache.catalina.connector.OutputBuffer.realWriteBytes(OutputBuffer.java:364)
at

org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Unknown Source)