Some tokens in client handshake data can be empty strings.

[Claus1]

I use flutter and some tokens that come from flutter IOWebSocketChannel.connect are empty string.

 def _opening_handshake(self, client, data):
      ...
        for token in tokens[1:]:            
                label, value = token.split(": ", 1)
     ...

this code causes an exception. a token can be empty.

[Haegi]

I will fix that. But does flutter send the empty token after it established the connection or while it is trying to connect?

[Claus1]

I tried to use Websock with flutter but even could not send and receive a message. After fixing uppercase header fields in Websock sources it anyway reported about closed connection. It seems indigestible bugs in flutter.
I used such Websock

from websock import WebSocketServer
from manager import *
import traceback
callback = None
def on_data_receive(client, rawdata):
    '''Called by the WebSocket server when data is received.'''
    global callback
    try:
        if not rawdata: 
            print('empty rawdata!')
            return
        data = json.loads(rawdata)
        if callback:
            if (data[0] == 'root' and data[1] is None):
                GuiServer.callback = None
                return                    
            else:
                result = callback(data[1]) #data[1] == returned value
                GuiServer.callback = None 
                if result is None:
                    result = process(data) # rise up                   
        else:
            result = process(data)       
        if result:
            if type(result) == Dialog:
                callback = result.callback
            ws.send(client, jsonString(prepareResult(result)))
    except Exception as e:            
        print(e,traceback.format_exc())
def on_connection_open(client):
    '''Called by the WebSocket server when a new connection is opened.'''
    ws.send(client,jsonString([menu,get_screen()]))   
def on_error(exception):
    """Called when the server returns an error
    """
    print(f'on_error: {exception}')   
def on_connection_close(client):
    """Called by the WebSocketServer when a connection is closed."""
    #ws.send(client, "Closing socket")
    print(client, 'closed')
def on_server_destruct():
    """Called immediately prior to the WebSocketServer shutting down."""
    pass
ws = WebSocketServer("127.0.0.1", 1234, 
                    on_data_receive=on_data_receive,
                    on_connection_open=on_connection_open, 
                    on_error=on_error, 
                    on_connection_close=on_connection_close)
ws.serve_forever()