TypeError: can only concatenate str (not "bytes") to str (engineio.payload.encode)

[umutdz]

Hello, I am using fastapi and python-socketio for Socket Server. Packages are below;

fastapi==0.103.1
uvicorn==0.27.0
python-socketio==5.11.0
pydantic-settings==2.0.3
pydantic==2.3.0
motor==3.3.1
pytz==2023.3.post1
requests==2.31.0
python-engineio==4.8.2

Sometimes, an error is raised when a client connects to the server, as shown below:

TypeError: can only concatenate str (not "bytes") to str

The second error is always raised as shown below:
Exception message: KeyError: 'Session is disconnected'
Culprit: engineio.base_server._get_socket

When attempting to connect to the server, clients sometimes encounter an error. Since this issue does not always occur, I am uncertain of what steps to take next. If anyone has any advice, please let me know.

[miguelgrinberg]

There is a FastAPI example in this repo. Try that and if that works, then compare it against yours to find what you've done differently.

Also please include a complete stack trace. The sections you've included are unrelated to the problem.

[miguelgrinberg]

How does the client connect? What data does it send after connection, if any?

[umutdz]

Client only listens to messages from the server upon entering a room - it does not send messages.

And client also use socketio with js

[miguelgrinberg]

Unfortunately this screenshot does not capture the beginning of the communication. You can see it yourself that what the screenshot is showing is the client sending and not receiving any response from the server.

Maybe you want to create a small and complete example that I can see to troubleshoot this? I have to think this is likely an error on your part, but with the bits that you've shown me I cannot pinpoint what is the error.

[umutdz]

I am confused. The client has connected and sent transport requests as mentioned before, but some of them are getting errors. Do you have any advice?

[miguelgrinberg]

Without details I cannot provide advice. If there are errors you need to show me all the details. Stack traces, logs, everything. See the troubleshooting section of the documentation if you don't know how to enable logging, then capture a complete session from the connection up to and including any errors.

Also, I want to note that you have completely ignored my request of making a small and complete application that I can use to debug this problem for you.