FIX/ENH: local mode based on nodejs implementation

[klauer]

Description

Enable client communication with the ADS server running on localhost for TwinCAT BSD systems.

Motivation and Context

• Communication with a local ADS server (i.e., on localhost) requires that you reserve a port from the router (and hopefully release it when you're done)
• I may be wrong, but it does not appear that this is implemented in Beckhoff's reference implementation
• I think the author of a nodejs ADS client figured this out, which is the reference implementation for this fix: https://github.com/jisotalo/ads-client/ (this has since been at least partially propagated to the rust client ads-rs though I'm not sure if it cleared it after use)
  • nodejs reference: registration, unregistration
  • Rust reference: https://github.com/birkenfeld/ads-rs/blob/7d4ca8a81f86e2fac14432c39df9ec20d352ab99/src/client.rs#L219-L230
  • Beckhoff/ADS reference: ? (*)

(*) If we want to get ads-ioc working on TwinCAT/BSD through linuxemu we're going to have to replicate this there somehow.

How Has This Been Tested?

• Only briefly on a TcBSD VM

Where Has This Been Documented?

This PR

Screenshots (if appropriate):

[TCBSD: RUN] [Administrator@test-plc-01  ~]$ ~/.local/bin/ads-async --log DEBUG get --our-net-id 127.0.0.1.1.1 --net-id 192.168.2.193.1.1 127.0.0.1  MAIN.iCount
DEBUG:ads_async:main(**{'host': '127.0.0.1', 'symbols': ['MAIN.iCount'], 'net_id': '192.168.2.193.1.1', 'add_route': False, 'our_net_id': '127.0.0.1.1.1', 'our_host': '127.0.0.1', 'timeout': 2.0})
DEBUG:ads_async.protocol:Connecting...
DEBUG:ads_async.protocol:Connected
DEBUG:ads_async.protocol:Reserved local connection settings from router: 192.168.2.193.1.1 (port=15945)
DEBUG:ads_async.protocol:AmsTcpHeader(reserved=0, length=60)
DEBUG:ads_async.protocol:AoEHeader(target=192.168.2.193.1.1:851(R0_PLC_TC3), source=192.168.2.193.1.1:32997, command_id=<AdsCommandId.READ_WRITE: 9>, state_flags=<AoEHeaderFlag.ADS_COMMAND: 4>, length=28, error_code=0, invoke_id=101)
DEBUG:ads_async.protocol:AdsReadWriteRequest(index_group=<AdsIndexGroup.SYM_INFOBYNAMEEX: 61449>, index_offset=0, read_length=798, write_length=12, data=b'MAIN.iCount\x00')
DEBUG:ads_async.protocol:(AoEHeader(target=192.168.2.193.1.1:32997, source=192.168.2.193.1.1:851(R0_PLC_TC3), command_id=<AdsCommandId.READ_WRITE: 9>, state_flags=<AoEHeaderFlag.ADS_COMMAND|RESPONSE: 5>, length=104, error_code=0, invoke_id=101), AoEReadResponse(result=<AdsError.NOERR: 0>, read_length=96, data=b'`\x00\x00\x00@@\x00\x00\xf2\xdf\x05\x00\x02\x00\x00\x00\x02\x00\x00\x00\x08\x10\x00\x00\x0b\x00\x03\x00\x00\x00MAIN.iCount\x00INT\x00\x00\x95\x19\x07\x18\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x06\x01\x00\x05\x13pytmc\x00pv: PLC:TEST:iCount\x00\x00\x00\x00'))
DEBUG:ads_async.protocol:Handling AoEReadResponse(result=<AdsError.NOERR: 0>, read_length=96, data=b'`\x00\x00\x00@@\x00\x00\xf2\xdf\x05\x00\x02\x00\x00\x00\x02\x00\x00\x00\x08\x10\x00\x00\x0b\x00\x03\x00\x00\x00MAIN.iCount\x00INT\x00\x00\x95\x19\x07\x18\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x06\x01\x00\x05\x13pytmc\x00pv: PLC:TEST:iCount\x00\x00\x00\x00')
DEBUG:ads_async.protocol:AmsTcpHeader(reserved=0, length=60)
DEBUG:ads_async.protocol:AoEHeader(target=192.168.2.193.1.1:851(R0_PLC_TC3), source=192.168.2.193.1.1:32997, command_id=<AdsCommandId.READ_WRITE: 9>, state_flags=<AoEHeaderFlag.ADS_COMMAND: 4>, length=28, error_code=0, invoke_id=102)
DEBUG:ads_async.protocol:AdsReadWriteRequest(index_group=<AdsIndexGroup.SYM_HNDBYNAME: 61443>, index_offset=0, read_length=4, write_length=12, data=b'MAIN.iCount\x00')
DEBUG:ads_async.protocol:(AoEHeader(target=192.168.2.193.1.1:32997, source=192.168.2.193.1.1:851(R0_PLC_TC3), command_id=<AdsCommandId.READ_WRITE: 9>, state_flags=<AoEHeaderFlag.ADS_COMMAND|RESPONSE: 5>, length=12, error_code=0, invoke_id=102), AoEReadResponse(result=<AdsError.NOERR: 0>, read_length=4, data=b'\x0e\x00\x00\x01'))
DEBUG:ads_async.protocol:Handling AoEReadResponse(result=<AdsError.NOERR: 0>, read_length=4, data=b'\x0e\x00\x00\x01')
DEBUG:ads_async.protocol:AmsTcpHeader(reserved=0, length=44)
DEBUG:ads_async.protocol:AoEHeader(target=192.168.2.193.1.1:851(R0_PLC_TC3), source=192.168.2.193.1.1:32997, command_id=<AdsCommandId.READ: 2>, state_flags=<AoEHeaderFlag.ADS_COMMAND: 4>, length=12, error_code=0, invoke_id=103)
DEBUG:ads_async.protocol:AdsReadRequest(index_group=<AdsIndexGroup.SYM_VALBYHND: 61445>, index_offset=16777230, length=2)
DEBUG:ads_async.protocol:(AoEHeader(target=192.168.2.193.1.1:32997, source=192.168.2.193.1.1:851(R0_PLC_TC3), command_id=<AdsCommandId.READ: 2>, state_flags=<AoEHeaderFlag.ADS_COMMAND|RESPONSE: 5>, length=10, error_code=0, invoke_id=103), AoEReadResponse(result=<AdsError.NOERR: 0>, read_length=2, data=b'\xc5w'))
DEBUG:ads_async.protocol:Handling AoEReadResponse(result=<AdsError.NOERR: 0>, read_length=2, data=b'\xc5w')
DEBUG:ads_async.protocol:AmsTcpHeader(reserved=0, length=44)
DEBUG:ads_async.protocol:AoEHeader(target=192.168.2.193.1.1:851(R0_PLC_TC3), source=192.168.2.193.1.1:32997, command_id=<AdsCommandId.WRITE: 3>, state_flags=<AoEHeaderFlag.ADS_COMMAND: 4>, length=12, error_code=0, invoke_id=104)
DEBUG:ads_async.protocol:AdsWriteRequest(index_group=<AdsIndexGroup.SYM_RELEASEHND: 61446>, index_offset=16777230, write_length=0, data=b'')
{
    "MAIN.iCount": [
        30661
    ]
}

[klauer]

Test suite is hitting into pytmc changes in TMC handling, specifically from this PR:
pcdshub/pytmc#311 (AMSNETID was actually part of the discussion there 😁 )

Looks like ads-async needs to dig down into the base type for AMSNETID and represent it as a string of bytes. My recollection of my implementation here for this is rather hazy though so fixing the test suite may take a bit.

That said, there's still other stuff to be done:

1. Consider moving these magic numbers into constants
2. Consider switching to a structure for both of these non-AoE (AMS/ADS over Ethernet) packets
   a. I've never seen (well, my recollection again is fuzzy...) this string of bytes before in ADS comms so I'm not sure what to make of it. It seems like an inline/immediate control channel comm of sorts
3. Support this on the server end -> implying to move the support into the 'protocol' section of ads-async
4. Add tests of this to the test suite
5. Support user-specified "local mode" (instead of checking against the target IP of localhost or 127.0.0.1, let the user toggle it on)
6. (Fix the test suite as noted above)

[klauer]

@ZLLentz @tangkong this is still prototype-grade, but the library is prototype-grade as well. This is probably worth merging and then tagging.

[tangkong]

This may be my least informed green stamp in a while. may prototypes be prototype

[ZLLentz]

Looks useful, no reason to let it sit in limbo forever

[ZLLentz]

I'm going to merge and pretend like I don't care about the CI at all