Python Serial Port Extension / Bugs / #166 RFC2217 connections always fail

#166 RFC2217 connections always fail

Milestone: v2.7

Status: closed-fixed

Owner: Chris Liechti

Labels: None

Priority: 5

Updated: 2015-08-05

Created: 2014-07-28

Creator: TJ

Private: No

Also reported as Ubuntu bug:

https://bugs.launchpad.net/ubuntu/+source/python-serial/+bug/1349525

Trying to connect to an RFC2217 access server:

$ python -m serial.tools.miniterm -D rfc2217://10.254.1.143:4001/logging=debug
DEBUG:pySerial.rfc2217:enabled logging
INFO:pySerial.rfc2217:NOTIFY_MODEMSTATE: 30
could not open port 'rfc2217://10.254.1.143:4001/logging=debug': Remote does not seem to support RFC2217 or BINARY mode [we-BINARY:False(INACTIVE), we-RFC2217:True(ACTIVE)]

Examining the code it seems that RFC2217Serial.open() has an incorrect test for connection completion.

    # negotiate Telnet/RFC 2217 -> send initial requests
    for option in self._telnet_options:
        if option.state is REQUESTED:
            self.telnetSendOption(option.send_yes, option.option)
    # now wait until important options are negotiated
    timeout_time = time.time() + self._network_timeout
    while time.time() < timeout_time:
        time.sleep(0.05) # prevent 100% CPU load
        if sum(o.active for o in mandadory_options) == len(mandadory_options):
            break
    else:
        raise SerialException("Remote does not seem to support RFC2217 or BINARY mode %r" % mandadory_options)

The problem is the " == len(mandadory_options)" test. The mandadory_options array has 2 elements, but since only state == REQUESTED will be sent in the prior 'for' loop one of them remains INACTIVE and therefore active == False, but the test compares against a count of the active options which reduces to

        if 1 == 2

which will therefore always fall through to the SerialException.

summing on options that are not INACTIVE allows the connection to be established:

       if sum(o.active for o in mandadory_options) == sum(o.state != INACTIVE for o in mandadory_options):

$ python -m serial.tools.miniterm -D rfc2217://10.254.1.143:4001/logging=debug
DEBUG:pySerial.rfc2217:enabled logging
INFO:pySerial.rfc2217:NOTIFY_MODEMSTATE: 30
DEBUG:pySerial.rfc2217:ENTER process_incoming( ECHO REQUESTED 0)
DEBUG:pySerial.rfc2217:LEAVE process_incoming( ECHO INACTIVE 0)
DEBUG:pySerial.rfc2217:ENTER process_incoming( we-SGA REQUESTED 0)
DEBUG:pySerial.rfc2217:LEAVE process_incoming( we-SGA INACTIVE 0)
DEBUG:pySerial.rfc2217:ENTER process_incoming( they-SGA REQUESTED 0)
DEBUG:pySerial.rfc2217:LEAVE process_incoming( they-SGA REQUESTED 0)
DEBUG:pySerial.rfc2217:ENTER process_incoming( we-SGA INACTIVE 0)
DEBUG:pySerial.rfc2217:LEAVE process_incoming( we-SGA INACTIVE 0)
DEBUG:pySerial.rfc2217:ENTER process_incoming( they-SGA REQUESTED 0)
DEBUG:pySerial.rfc2217:LEAVE process_incoming( they-SGA INACTIVE 0)
DEBUG:pySerial.rfc2217:ENTER process_incoming( they-RFC2217 REQUESTED 0)
DEBUG:pySerial.rfc2217:LEAVE process_incoming( they-RFC2217 ACTIVE 1)
DEBUG:pySerial.rfc2217:ENTER process_incoming( we-RFC2217 REQUESTED 0)
DEBUG:pySerial.rfc2217:LEAVE process_incoming( we-RFC2217 REQUESTED 0)
DEBUG:pySerial.rfc2217:ENTER process_incoming( they-RFC2217 ACTIVE 1)
DEBUG:pySerial.rfc2217:LEAVE process_incoming( they-RFC2217 ACTIVE 1)
DEBUG:pySerial.rfc2217:ENTER process_incoming( we-RFC2217 REQUESTED 0)
DEBUG:pySerial.rfc2217:LEAVE process_incoming( we-RFC2217 ACTIVE 1)
INFO:pySerial.rfc2217:Negotiated options: [ECHO:False(INACTIVE), we-SGA:False(INACTIVE), they-SGA:False(INACTIVE), they-BINARY:False(INACTIVE), they-RFC2217:True(ACTIVE), we-BINARY:False(INACTIVE), we-RFC2217:True(ACTIVE)]
DEBUG:pySerial.rfc2217:SB Requesting baudrate -> '\x00\x00%\x80'
DEBUG:pySerial.rfc2217:SB Requesting datasize -> '\x08'
DEBUG:pySerial.rfc2217:SB Requesting parity -> '\x01'
DEBUG:pySerial.rfc2217:SB Requesting stopsize -> '\x01'
DEBUG:pySerial.rfc2217:Negotiating settings: [stopsize:REQUESTED, parity:REQUESTED, baudrate:REQUESTED, datasize:REQUESTED]
DEBUG:pySerial.rfc2217:SB Answer baudrate -> '\x00\x00%\x80' -> ACTIVE
DEBUG:pySerial.rfc2217:SB Answer datasize -> '\x08' -> ACTIVE
DEBUG:pySerial.rfc2217:SB Answer parity -> '\x01' -> ACTIVE
DEBUG:pySerial.rfc2217:SB Answer stopsize -> '\x01' -> ACTIVE
INFO:pySerial.rfc2217:Negotiated settings: [stopsize:ACTIVE, parity:ACTIVE, baudrate:ACTIVE, datasize:ACTIVE]
DEBUG:pySerial.rfc2217:SB Requesting control -> '\x01'
DEBUG:pySerial.rfc2217:SB Answer control -> '\x01' -> ACTIVE
INFO:pySerial.rfc2217:NOTIFY_MODEMSTATE: 1
INFO:pySerial.rfc2217:set RTS to active
DEBUG:pySerial.rfc2217:SB Requesting control -> '\x0b'
DEBUG:pySerial.rfc2217:SB Answer control -> '\x0b' -> ACTIVE
INFO:pySerial.rfc2217:set DTR to active
DEBUG:pySerial.rfc2217:SB Requesting control -> '\x08'
DEBUG:pySerial.rfc2217:SB Answer control -> '\x08' -> ACTIVE
DEBUG:pySerial.rfc2217:SB Requesting purge -> '\x01'
DEBUG:pySerial.rfc2217:SB Answer purge -> '\x01' -> ACTIVE
DEBUG:pySerial.rfc2217:SB Requesting purge -> '\x02'
DEBUG:pySerial.rfc2217:SB Answer purge -> '\x02' -> ACTIVE
--- Miniterm on rfc2217://10.254.1.143:4001/logging=debug: 9600,8,N,1 ---
--- Quit: Ctrl+] | Menu: Ctrl+T | Help: Ctrl+T followed by Ctrl+H ---

Discussion

Chris Liechti - 2014-07-31

OK fix committed. Though that also seems to be a problem with the RFC-2217 server you are using because the code was working with other servers. But it seems that those RFC-2217 servers all work slightly different...

If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
- Pavel - 2015-01-28
  
  It's broken in 2.7 for the example rfc2217 server scripts provided with PySerial.
  
  If you would like to refer to this comment somewhere else in this project, copy and paste the following link:

Chris Liechti - 2014-07-31

status: open --> pending-fixed

assigned_to: Chris Liechti
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:

Chris Liechti - 2015-08-05

status: pending-fixed --> closed-fixed
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:

RFC2217 connections always fail

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#166 RFC2217 connections always fail

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