Initializing a Modbus Master uses CONFIG_FMB_TCP_PORT_DEFAULT instead of mb_communication_info_t config.tcp_opts.port (EPROT-21)

[ivobelitz]

Checklist

• Checked the issue tracker for similar issues to ensure this is not a duplicate
• Read the documentation to confirm the issue is not addressed there and your configuration is set correctly
• Tested with the latest version to ensure the issue hasn't been fixed

How often does this bug occurs?

always

Expected behavior

During initialization of a Modbus Master, the port value set in .tcp_opts.port in the mb_communication_info_t struct is used.

Actual behavior (suspected bug)

The value of CONFIG_FMB_TCP_PORT_DEFAULT is used

Error logs or terminal output

Steps to reproduce the behavior

1. Set CONFIG_FMB_TCP_PORT_DEFAULT to port X
2. When initializing a Modbus master, set mb_communication_info_t.tcp_opts.port to port Y
3. Open a TCP server on port X and observe that packets are arriving there

Project release version

v2.1.1

System architecture

ARM 64-bit (Apple M1/M2, Raspberry Pi 4/5)

Operating system

MacOS

Operating system version

Sequoia 15.6.1

Shell

ZSH

Additional context

No response

[ivobelitz]

Update: I see that setting an IP should be done through the slave_ip_address_table instead. Still, I find it very confusing that the examples are using .tcp_opts.port, which from what I understand is not taken into account.
I also do not fully understand what the meaning behind the 01 and 02 that are prepended to the IP string:

"01;192.168.1.21",      // Address corresponds to UID (slave address) = MB_DEVICE_ADDR1 and set to predefined value by user
"02;192.168.1.22",      // Address corresponds to MB_DEVICE_ADDR2 of slave device in the Modbus data dictionary

[alisitsyn]

The original approach is to use the default port settings defined in the structure for created instance. So, if the port is not defined for slave in the address table the default settings from structure may be inherited. This does not mean the slaves must inherit the default port settings from master but it is logically correct to get it from global project setting CONFIG_FMB_TCP_PORT_DEFAULT. If for some reason the slave needs to get port settings explicitly, it is possible to set it explicitly in the address configuration string.

Update: I see that setting an IP should be done through the slave_ip_address_table instead. Still, I find it very confusing that the examples are using .tcp_opts.port, which from what I understand is not taken into account.
I also do not fully understand what the meaning behind the 01 and 02 that are prepended to the IP string:

As described in the comment and in the esp-modbus documentation, the prepended field is the UID of the slave.

The issue is confirmed with minor severity and will go through the formal process. This will be fixed or not according to final decision.