Added Modbus TCP proxy

[andrei-lazarov]

Related to #98

Hello! I needed proper TCP frames for systems that don't support the 'RTU over TCP' messages provided by solarman_rtu_proxy.py.

So I added the solarman_tcp_proxy.py utility.

It works pretty well.

I do get errors sometimes (on both proxies), but it's probably a bad connection..
I am connected remotely through port forwarding.

ERROR: request ask for transaction_id=31 but got id=28, Skipping
ERROR: request ask for transaction_id=31 but got id=29, Skipping

Would love to hear some feedback.

[githubDante]

Hi,

We have umodbus as a dependency and I think it is better to use the CRC methods from there

from umodbus.client.serial.redundancy_check import get_crc

Also do not use the UnitId as SlaveId they are not the same. It will work if you use 1 which is the default for most inverters, but will fail with any other value. If the proxy must service more than one inverter the UnitId must be mapped to the correct PysolarmanV5 instance.

[andrei-lazarov]

Thanks!
I changed it to use the provided crc method.

Well the proxy requires IP and serial from the inverter, so it can only serve one, right?
You mean - if I connect multiple inverters, through multiple proxies, to HA for example - each will get a different UnitId from HA: 1, 2, 3..
So should I hard-code the SlaveId to 1 like in did in the last commit?

[githubDante]

You mean - if I connect multiple inverters, through multiple proxies, to HA for example - each will get a different UnitId from HA: 1, 2, 3..
So should I hard-code the SlaveId to 1 like in did in the last commit?

I don't use HA, so I can't comment on that, but you can have a map/dict even in this state of the proxy and to instantiate different client for different unitId. The slaveId for all however should be 1.
We use it (0x1) as a default value (see the PysolamanV5.__init__/mb_slave_id) but the modbus frame stays untouched by the send_raw_modbus_frame method, so the slaveId should already be there.

[andrei-lazarov]

Thanks. Fixed, the tests pass now

[githubDante]

I see. Thank you!