What is the fastest way to send commands to Raspberry Pi over ethernet?

Question

I'm working on a IoT project. The idea is basically: I have a notebook running a Python program that get frames from an IP camera, process it, and based on the result change a Raspberry Pi GPIO pin state. The computer, the camera and the Pi are connected to the same wireless router (by cables).

I was trying to use Paramiko to execute the commands on the raspPi, but I got problem with the velocity. The camera FPS is bigger than Paramiko could provide. I also tried parallel-ssh library (https://parallel-ssh.org/post/ssh2-python/) but still not fast enough.

Do you have an ideia to help me on this problem?

Thank you!

Answer 1

Create a UDP "server" socket on the Pi, and use a client on the laptop to send commands to it. Just send more packages to be sure to get it. UDP won't need you to connect, and it has good latency. Or you can use TCP as well, it's not that different on the Python side.

Since you probably wrote your image recognition program in Python (and added a Python tag), I wrote a simple example (all right, copy-pasted from a project I copy-pasted from somewhere):

Server side:

import socket

UDP_IP = "0.0.0.0" # listen to everything
UDP_PORT = 12345 # port

sock = socket.socket(socket.AF_INET,socket.SOCK_DGRAM)
sock.bind((UDP_IP, UDP_PORT))

while True:
  data, addr = sock.recvfrom(512) # random buffer size, doesn't matter here..
  print("received message:", data)
  #simplest way to react.. of course, a better parser should be used, and add GPIO code, etc..
  if data==b'LED=1\n':
    print("LED ON")
  elif data==b'LED=0\n':
    print("LED OFF")

Client:

import socket
import time

UDP_IP = "127.0.0.1" # set it to destination IP.. RPi in this case
UDP_PORT = 12345

print("UDP target IP:", UDP_IP)
print("UDP target port:", UDP_PORT)

sock = socket.socket(socket.AF_INET,socket.SOCK_DGRAM)

while True:
  print("Turn ON")
  sock.sendto(b'LED=1\n', (UDP_IP, UDP_PORT))
  time.sleep(2)
  print("Turn OFF")
  sock.sendto(b'LED=0\n', (UDP_IP, UDP_PORT))
  time.sleep(2)

You could use broadcast to flood everything in your LAN as well.. but RPi gets your message whatever its address is. Also, I added newlines to the protocol, so you can simply test in in netcat: nc -u localhost 12345 then type LED=0 and press Enter.

Answer 2

If you are looking for a workable solution using Python https://gpiozero.readthedocs.io/en/stable/remote_gpio.html has instructions for remote GPIO.

You could roll your own custom solution using any networking protocol, although sockets are probably the most common, but overkill for a simple task.