How do I use commandPort?

[Henrik_Cederblad]

I wish to get started using Maya's commandPort on Windows in order to trigger external (MEL) commands from my Elgato Stream Deck. My only issue is, I'm really not a programmer and I don't know how to set it up.

I'm primarily looking for the MEL method, but a Python version would also be relevant. Here's my Python info:

>>> sys.version
'3.9.5 (tags/v3.9.5:0a7dcbd, May 3 2021, 17:27:52) [MSC v.1928 64 bit (AMD64)]'
>>> sys.executable
'C:\\Python39\\python.exe'

How do I do this? 🙂

[Henrik_Cederblad]

Since there's been no reply, I'll fill in the details I've gathered so far. Still haven't got it to work as I'm getting a TypeError when executing a command, but maybe someone can help me understand if this is a bug in Maya or something I can work around?

1. Create a userSetup.mel if you haven't got one already (could be py also, but we'll stick with .mel here) in 

C:\Users\<user>\Documents\maya\<mayaversion>\scripts

2. Add the following inside that file (you may change the port numbers to anything you like):

commandPort -name "localhost:7001" -sourceType "mel" -echoOutput;
commandPort -name "localhost:7002" -sourceType "python" -echoOutput;

3. Then create a Python file (in this example I'll call it commandPort_Template.py). Note: As I wish to send MEL commands, I'll use the MEL port (7001) as assigned in Step 2):

import socket
HOST = '127.0.0.1'
PORT = 7001
ADDR=(HOST,PORT)
def SendCommand():
client = socket.socket (socket.AF_INET, socket.SOCK_STREAM)
client.connect(ADDR)
command = 'polyCube'
client.send(command)
client.close()

if __name__=='__main__':
SendCommand()

4. Run the Python file. In my case, I run it like so:

"C:\Python39\python.exe" "D:\3D\Maya\SCRIPTS\commandPort_Template.py"

That should work, but it doesn't. As said, I'm getting a TypeError when sending the command to Maya:

# # File "C:\Program Files\Autodesk\Maya2022\Python37\lib\socketserver.py", line 720, in __init__
self.handle()
# TypeError: a bytes-like object is required, not 'str'
# ----------------------------------------
# ----------------------------------------
# Exception happened during processing of request from ('127.0.0.1', 54756)
# Traceback (most recent call last):
# # File "C:\Program Files\Autodesk\Maya2022\Python37\lib\socketserver.py", line 316, in _handle_request_noblock
self.process_request(request, client_address)
# # File "C:\Program Files\Autodesk\Maya2022\Python37\lib\socketserver.py", line 347, in process_request
self.finish_request(request, client_address)
# # File "C:\Program Files\Autodesk\Maya2022\Python37\lib\socketserver.py", line 360, in finish_request
self.RequestHandlerClass(request, client_address, self)
# # File "C:\Program Files\Autodesk\Maya2022\Python37\lib\site-packages\maya\app\general\CommandPort.py", line 134, in handle
self.wfile.write(self.server.commandMessageQueue.get() + self.resp_term)
# # File "C:\Program Files\Autodesk\Maya2022\Python37\lib\socketserver.py", line 799, in write
self._sock.sendall(b)

[Henrik_Cederblad]

Someone, please! I'm so close being able to use my Stream Deck to send commands to Maya, removing the necessity to use hotkeys, which I've ran out of since long ago ... How do I get past this error?! (Sorry for the bold text.)

[Henrik_Cederblad · Accepted solution]

For anyone looking how to use commandPort, I'm happy to report that I've got a working solution that won't give any TypeErrors (which my previous attempts gave) and now I can use my Stream Deck XL rather than running out of hotkeys for all my commands and scripts. This more or less makes Maya's shelves redundant also.

1. I've created a userSetup.py file here: <drive>:\<yourusername>\Documents\maya\<20XX>\scripts\userSetup.py

2. In userSetup.py, I'ved added these lines:

import maya.cmds as cmds
cmds.commandPort(name=":54321", sourceType="mel")
cmds.commandPort(name=":54322", sourceType="python")

Note: Someone told me it can be a good idea to open the commandPorts using evalDeferred, like so:

cmds.evalDeferred('cmds.commandPort(name=":54321", sourceType="mel")')
cmds.evalDeferred('cmds.commandPort(name=":54322", sourceType="python")')

Which, according to the person I talked to, was to make sure it's executed at the correct time.

3. Then I've created a first template_command.py file with the following (creating a cube):

import socket

HOST = '127.0.0.1'  # the local host
PORT = 54322  # The same port as used by the server
ADDR = (HOST, PORT)


def send_command():
    client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    client.connect(ADDR)
    command = 'cmds.polyCube()'

    message = command
    client.send(str.encode(message))
    data = client.recv(1024)  # receive the result info
    client.close()

    print(data)


if __name__ == '__main__':
    
    # Run this within Maya to open the ports. The port can be any 5 digits
    """
    import maya.cmds as cmds
    cmds.commandPort(name=":54322", sourceType="python")
    """
    
    send_command()

4. (N.B. Windows only). To prevent a momentary console window popping up when execiting scripts, I've renamed the script so that it has the .pyw suffix rather than .py, e.g. changed template_command.py to template_command.pyw. There are other ways to accomplish this in UNIX OSes like macOS and Linux by instead keeping the .py extension and first chmod +x template_command.py ot make it executable without invoking it via a Python interpreter and then adding a shebang like #!/usr/bin/python (there are variations to this shebang line that allows better control over which Python executable you're running, etc. but I won't go into that here) at the very first line in the script.

That's it!

Note: the above pertains to >Maya 2022.3 which uses Python3. If you're on older Maya versions, they use Python2 and the code might have to be tweaked to worked for that Python version first.

[fedepuopolo]

Hi, thanks for sharing this. I'm trying to implement it but following these steps Maya opens a new scene and I'm getting an error "Unrecognized file type" when doing double click on template_command.pyw (same if I drag that file to my viewport). 

For my userSetup.py I tried both version, with and without evalDeferred. And I also set the security to off in Maya's preferences.

Any advice on how to make this work?

Thanks!