Python WebSocket send() does not received on Java server (tomcat)

Question

I have java application running on Tomcat server. It works normally with Android/iOS/Web application. After logged in using username and password, the server will generate a token and the application use the token to establish websocket connection with server to receive and send message from/to server.

To receive a broadcast from the server, the application need to send a message to the server telling message code they want to subscribe.

Now, I want to implement python (version 3.9.6) application to receive and send message from/to the server. To make it easy in the first place, I skip the logged in process by logged in using postman and hard-coded token.

In the first try, I use library websockets

import asyncio
import websockets

# Define the WebSocket URL
async def connect_and_listen(url, headers):
    print("called connect_and_listen")
    async with websockets.connect(url, extra_headers=headers) as websocket:
        print("called websockets.connect")
        # Send Subscribe
        try:
            await websocket.send("A_BINARY_MESSAGE")
        except Exception as e:
            print(e)

        print("while true")
        # Loop Receive Broadcast
        while True:
            # Receive data from the WebSocket server
            data = await websocket.recv()
            # Update Excel with the received data using PyXLL functions
            update_excel(data)

def update_excel(data):
    print(data)

url = "ws://localhost:8080/BCST_PATH"
token = "TOKEN"
auth_token = "Bearer " + token
headers = {"Authorization": auth_token}


asyncio.get_event_loop().run_until_complete(connect_and_listen(url, headers))

The result is I did not receive any broadcast from server. So I decided to change library to websocket-client

import websocket

url = "ws://localhost:8080/BCST_PATH"
token = "TOKEN"
auth_token = "Bearer " + token
headers = {"Authorization": auth_token}

ws = websocket.WebSocket()
ws.connect(url, header=headers)

ws.send("A_BINARY_MESSAGE")
print ("Receiving...")
resp = ws.recv()
print ("Receive: %s", resp)
ws.close()

Still not working. I debugged in the Java application and it does not receive any message from client (both case).

I tried the same flow with the same url, token, and binary message using Postman and it works. I am out of idea what's wrong in my code.

Answer 1

Finally I found the solution. I use the 2nd code which using websocket-client library. Adding websocket.ABNF.OPCODE.BINARY makes it works!

ws.send("A_BINARY_MESSAGE", websocket.ABNF.OPCODE_BINARY)