Edge case uncaught exception in fjagepy send

[impala454]

We encountered an issue with fjagepy where, when sending a message via transport. We think this happened when the modem was disconnected during a send operation and the offending line is here. Trace looked like this:

[action_agent-1]     self.transport.send(datagram_req)
[action_agent-1]   File "/usr/local/lib/python3.10/dist-packages/fjagepy/__init__.py", line 147, in send
[action_agent-1]     self.owner.send(msg)
[action_agent-1]   File "/usr/local/lib/python3.10/dist-packages/fjagepy/__init__.py", line 760, in send
[action_agent-1]     self.socket.sendall((rq + '\n').encode())
[action_agent-1] BrokenPipeError: [Errno 32] Broken pipe

Looking at that code it appears it's using the standard Python socket.sendall() which says it will raise an Exception on error and return None on success. So perhaps a check here would be good before returning True so the user doesn't need to catch the underlying socket exceptions.

[notthetup]

Thanks @impala454. Let me take a look at this.

[impala454]

Here's a sample where I was able to reproduce this most of the time. Steps:

• change your IP/port to whatever your modem is
• power modem on until it's booted
• run the script
• power modem off
• script will eventually indefinitely hang at sending xxx (the transport.send() call)
• power modem back on
• once modem is booted back up the script will resume sending the same number XXX indicated in the hung call but fail with an exception which is caught by the script
• the script will automatically reconnect but on some runs an exception is printed to the screen but not re-raised or returned to the transport.send() call: Exception: [Errno 107] Transport endpoint is not connected .

The script:

#!/usr/bin/env python3

from time import sleep
from fjagepy import Gateway
from unetpy import TxFrameReq

modem_ip_address = "192.168.10.38"
modem_port = 1100
remote_modem_addr = 58
gateway = None
transport = None
reconnect = True
counter = 0

while True:
    if not gateway:
        reconnect = True
    elif not gateway.isConnected():
        print('disconnected')
        reconnect = True

    if reconnect:
        try:
            print('connecting')
            gateway = Gateway(hostname=modem_ip_address, port=modem_port)
        except Exception as ex:
            print(f'connect failed: {ex}')
            sleep(0.1)
            continue
        else:
            transport = gateway.agent('transport')
            reconnect = False
            print('connected')

    req = TxFrameReq()
    req.type = 2
    req.to = remote_modem_addr
    req.data = list(bytearray('\x00\x23\x04\x54\x65\x13\x05\x36\x76\x31\x12\x13\x07', encoding='utf-8'))

    print(f'sending {counter}')
    try:
        transport.send(req)
    except Exception as ex:
        print(f'lockup.py exception {counter}: {ex}')
        gateway.close()
        counter += 1
    else:
        print(f'sent {counter}')
        counter += 1

    sleep(0.1)

The main concerns here are two things:

• The gateway continues to report as connected and also the send call returns None and doesn't re-raise any exceptions, so the user has no way of knowing the modem is disconnected.
• The case where the Transport endpoint is not connected Exception occurs and is printed doesn't make it back to the user in any way except via the console print. So user software thinks the send() succeeded.