Sun Java System Web Server 7.0 Update 7 Performance Tuning, Sizing, and Scaling Guide

HTTP Listener (Listen Socket) Information

The following HTTP listener information includes the IP address, port number, number of acceptor threads, and the default virtual server. For tuning purposes, the most important field in the HTTP listener information is the number of acceptor threads.

You can have many HTTP listeners enabled for virtual servers, but at least one is enabled for your default server instance (usually The monitoring information available through the Admin Console does not show the HTTP listener information, because that information is available in the Admin Console on the configuration's HTTP Listeners tab.

The following is an example of how the HTTP listeners information appears in perfdump:

ListenSocket ls1:
Acceptor Threads          1
Default Virtual Server    https-test

If you have created multiple HTTP listeners, perfdump displays all of them.

To edit an HTTP listener using the Admin Console, for the configuration, select the HTTP Listeners tab. Click the listener name to edit the listener.

To configure an HTTP listener using the command-line interface, use the command wadm set-http-listener-prop.

For more information about adding and editing listen sockets, see the Sun Java System Web Server 7.0 Update 7 Administrator’s Guide.


The Address field contains the base address on which this listen socket is listening. A host can have multiple network interfaces and multiple IP addresses. The address contains the IP address and the port number.

If your listen socket listens on all network interfaces for the host machine, the IP part of the address is


This setting is tunable when you edit an HTTP listener. If you specify an IP address other than, the server makes one less system call per connection. Specify an IP address other than for best possible performance.

Acceptor Threads

Acceptor threads are threads that wait for connections. The threads accept connections and put them in a queue where they are then picked up by worker threads. For more information, see Connection-Handling Overview.

Ideally, you want to have enough acceptor threads so that there is always one available when a user needs one, but few enough so that they do not burden the system. A good rule is to have one acceptor thread per CPU on your system. You can increase this value to about double the number of CPUs if you find indications of TCP/IP listen queue overruns.


This setting is tunable when you edit an HTTP listener. The number of acceptor threads defaults to the number of CPUs on your system.

Other HTTP listener settings that affect performance are the size of the send buffer and receive buffer. For more information regarding these buffers, see your operating system documentation.

Default Virtual Server

Virtual servers work using the HTTP 1.1 Host header. If the end user’s browser does not send the Host header, or if the server cannot find the virtual server specified by the Host header, Web Server handles the request using a default virtual server. You can configure the default virtual server to send an error message or serve pages from a special document root.


This setting is tunable when you edit an HTTP listener.