KEEPALIVE (JANUS DEFINE parameter)

<section begin="desc" />KEEPALIVE xxxx &mdash; number of seconds to hold open TCP/IP connection.<section end="desc" />

KEEPALIVE is a parameter on JANUS DEFINE, which defines and sets characteristics of a Janus port.

The KEEPALIVE parameter indicates the number of seconds a TCP/IP connection is to be held open after an HTTP request on that connection. KEEPALIVE must be followed by a single number between 0 and 32767, which indicates the maximum number of seconds to hold the connection open. A setting of 0 means no keep-alive.

For WEBSERV ports, this parameter tells Janus Web Server to keep HTTP connections from a client (often a browser) open for the indicated period of time. For CLSOCK ports, KEEPALIVE tells Janus Sockets to keep an HTTP connection to a web server open for the indicated period of time, and to reuse that connection for other requests to the same server.

Keep-alive connections, more often referred to as persistent connections, can reduce network traffic and, more significantly, HTTP request latency. Both of these benefits are magnified for SSL connections, where each HTTP request requires a TCP/IP and SSL connection-establishment handshake.

For a Janus Web Server connection to be held open, the client/browser must indicate that it supports HTTP keep-alives. For a Janus Sockets connection to be held open, the web server must indicate that it supports HTTP keep-alives. Most modern browsers and web servers support and take advantage of keep-alives.

The KEEPALIVE parameter is valid only for Janus Web Server and for Janus Sockets CLSOCK ports used for HTTP traffic (that is, not for SMTP connections). It is not valid for Janus Sockets SRVSOCK or DEBUGGERCLIENT ports and not valid for SMTP connections.

KEEPALIVE is new as of Sirius Mods Version 6.8.

See also

• List of Janus commands
• List of JANUS DEFINE parameters