Programming Jabber

Standard I/O (STDIO)

The TCP sockets component connect method is used to connect an external component to the Jabber backbone via a socket connection through which streamed XML documents are exchanged. There is another way for components to connect and exchange XML document streams with the Jabber backbone—using the STDIO connection method.

While the TCP sockets method requires external components to be independently started and stopped, the STDIO method represents a mechanism whereby the jabberd process starts the external component itself. The component to start is specified inside an <exec/> tag. (Indeed the STDIO method is also known as the exec method.) Example 4-6 shows how the STDIO method is specified in the configuration.

Example 4-6. Invoking an external component with STDIO

<exec>/path/to/component.py -option a -option b</exec>

Here we see that the component is a Python program and is being passed some switches at startup.

So where’s the socket connection in this method? There isn’t one. The XML documents are exchanged through standard I/O (STDIO). The component writes XML fragments to STDOUT, and these are received on the Jabber backbone. The component receives XML fragments destined for it on STDIN, fragments that are written out from the Jabber backbone.

Just as a component connected using the TCP sockets method sends an opening document fragment, the component connected with this STDIO method sends an opening document fragment to initiate a connection and conversation: ...