a shared pixel display controllable via TCP

Dependencies: ocaml 5.0, tsdl

$ dune exec -- server/localnet/server.exe
# in another terminal, try one of the basic clients:
$ dune exec -- client/client.exe
# or go write your own!

Pass --help to the server binary for additional settings.

protocol

The server expects TCP packets. An TCP packet should contain one or several concatenated pixel commands. A pixel command consists of 7 bytes, and tells the server to draw one colored pixel:

 XX YY R G B 

• XX: a 16 bits big-endian integer for the x coordinate of the pixel
• YY: a 16 bits big-endian integer for the y coordinate of the pixel
• R, G, B: the color of the pixel (the red, green, blue component respectively)

anti-spam measures (for server/localnet)

The localnet server implements some basic rate-limiting / anti-spam measures based on the client IP address, tweakable using the --nb-clients and --max-age options of the server.

• there is a limit on the number of visible pixels sent by the same client; after this limit, oldest pixels get removed first. If --nb-clients (an estimation of the number of simultaneous clients) is N and the total number of pixels of the screen is S, then the per-client limit is S / N.

• pixels decay and disappear after some time (set by --max-age).

separate receiver/display

The server/receiver and server/display components are an alternative to server/localnet.

They make it possible to decouple listening for clients and displaying. The receiver (contacted by clients and receiving pixels packets) can be put on a different computer than the display. The output of the receiver should be piped into the input of the display component, which can e.g. be done through ssh.

Example usage:

scp _build/default/server/receiver/receiver.exe you@yourserver
ssh you@yourserver ./receiver.exe | dune exec -- server/display/display.exe

NB: be aware that ^C-ing the ssh command will not automatically terminate the receiver process on the remote server, you may have to kill it separately.