Terminal sessions you can bookmark

Summary

Zellij is a terminal workspace and multiplexer. One of the unique traits of terminal multiplexers is their ability to keep sessions alive in the background without a terminal attached to them. In the recent Zellij version we released a built-in web client, allowing users to attach to these sessions from the browser - essentially making a dedicated terminal application optional. In this post we’re going to take a look at how we built the Zellij Web Terminal: which technologies we used, how we architected the solution and some challenges we faced along the way. What we have Keeping sessions alive in the background involves a client/server architecture. The client runs in the user’s terminal like any other program and communicates over IPC with a server holding the state of the terminal session (open programs, pane and tab layout, etc.) When Zellij first starts, the client spawns a new server process and daemonizes it so that it keeps running independently in the background. The client passes user input (keystrokes and mouse events) to the server, and the server passes render instructions to the client. When the client detaches from the server, the server remains alive until the client connects again. The Goal To allow the browser to act as a Zellij client, we would need: A terminal emulator able to run inside the browser A web-server able to both serve this emulator and interact with the Zellij server Architecting the solution We elected to have a single web-server per machine, able to serve multiple sessions to multiple clients. Reusing the Zellij client code per connection, serving as a translation layer between the browser’s websockets and the Zellij server’s IPC channels. This would mean that there’s only one web-server per machine - making administration easier while still allowing multiple-session operations per browser client. Since browser clients - through the web-server - will be connected to the same IPC channels as terminal clients, they appear as regular ...