Implementation

The GraphTerm server written in pure python, using the Tornado web framework, with websocket support. The GraphTerm client uses standard HTML5+Javascript+CSS (with jQuery).

The GraphTerm server may be run on your desktop or on a remote computer. Users create and access terminal sessions by the connecting to the Graphterm server on port 8900, either directly or through SSH port forwarding. By default, the localhost on the computer where the GraphTerm server is running is available for opening terminal sessions. Other computers can also connect to the GraphTerm server, on a different port (8899), to make them accessible as hosts for connection from the browser.

A pseudo-tty (pty) is opened on the host for each terminal session. By setting the PROMPT_COMMAND environment variable, GraphTerm determines when the stdout of the previous command ends, and the prompt for the new command begins.

The connection between the browser and the GraphTerm server is implemented using websockets (bi-directional HTTP). The GraphTerm server acts as a router sending input from controlling browser terminal sessions to the appropriate pty on the host computer, and transmitting output from each pty to all connected browser terminal sessions.

GraphTerm extends the xterm terminal API by adding a new control sequence for programs to transmit a CGI-like HTTP response through standard output (via a websocket) to be displayed in the browser window. GraphTerm-aware programs can interact with the user using HTML forms etc.