Agent TCP4 not responding to RMW stream or packet

## Issue template

- Hardware description:
Agent running on Ubuntu 22.04 x86)64
Firmware on Raspberry PI Pico W
- RTOS: FreeRTOS
- Installation type: micro_ros_setup
- Version or commit hash: Humble

#### Steps to reproduce the issue
Agent running in TCP4 mode:
$ ros2 run micro_ros_agent micro_ros_agent tcp4 -p 8000

Firmware is using LWIP Sockets under Freertos as a custom transport rmw (rmw_uros_set_custom_transport). Tested both stream and packet communication modes.

#### Expected behavior
Would expect some acknowledge package or activity from the Agent.

#### Actual behavior
Agent is listening on port 8000. It accepts the connection. Data is sent from the firmware to the Agent but no response from the agent.

#### Additional information

I've not managed to find any blogs or code examples using tcp4 comms on the Agent. Can I confirm that this does talk rmw and whether this should be stream or packet mode?

Start with the micro_ros_agent tcp4 -p 8000 command and the firmware's rmw_uros_set_custom_transport configuration using LWIP sockets on FreeRTOS. Compare stream and packet communication and verify whether the Agent responds to the firmware data; document the required mode or reproduce a confirmed fix.

Written by the indexing model from the issue text.