websocket

Installation

Server and client

After cloning, virtual environment with python3 needs to be created.

Create virtual environment with python3 and requirements file:

virtualenv ~/venv/socket -p python3
source ~/venv/socket/bin/activate
pip install -r requirements.txt

Server side

ID associated with websockets

Normally, the designated user is nixWorker, and should be created if not present. nixWorker requires credentials to access the database (username, password) which should be provided in its .labkey/server.json file, refer to labkeyInterface documentation. Also, websockets will require nixSuite to be installed and pointed to by .labkey/setup.json.

Firewall

Script open_port.sh will program the firewall on server side to limit websockets to only work for a limited number of clients. Both server and client ip need to be provided in serviceScripts/env.sh.

To find IP address, run

ip add show

Select the IP address with interface that has the highest probability that it points to a physical interface rather than a docker connection. In most systems this is eth0.

The same call can be done on all clients that will be allowed to connect.

Run sudo open_port.sh to modify firewall to accept connection on the designated port.

Run serviceScripts/start.sh to start the server. Look for output/log at ~/logs/socketServer.log.

Client side

No install is required. No dependencies, since all communication is text only.

Testing

Client side

~/software/venv/socket/bin/python send.py server:TEST:1

Server side

Open port

To check whether packets from client reach the host, use

sudo tcpdump -i enp68s0 'tcp port 8000' -v

This prints traffic to port 8000, say. Also helpful for determining actual IP address of the request; sometimes the actual source is behind a firewall and the IP could be mangled.

This address should be added to the $IPCLIENT address list in env.sh for open_port.sh to allow connections.

Allowed origins

Websockets further limits allowed connections to clients listed in websocketServer.py. The origin is hardcoded as a single name in send.py and as a list in websocketServer.py. For the communication to work, the name from send.py should be a member of the websocketServer.py list.

The error associated with mis-configuration of origins is:

websockets.exceptions.InvalidStatusCode: server rejected WebSocket connection: HTTP 403

Features

Concurrence

Websocket will respond to any call submitted to the server with a separate invocation of the handler. This means that submitting multiple jobs will result in concurrent execution of all jobs, which might bog down the server. Websocket itself won't deal with scheduling, but the handler in websocketServer.py could be rewritten to delegate job handling to scheduler such as torque or slurm, should one run on the server.