OFDM Transceiver to send/receive messages

Hello,

I am trying to implement an OFDM transceiver using 2 USRP B200 in order to use each one of them as a chat client using message passing, in order to send and receive messages on both.
So far I have been able to make the communication working unidirectionally, so I can send a message and receive it on the other side.

Then I tried to merge my TX and RX flowgraphs into one having both to build a transceiver. Unfortunately I did not succeed to have a working flowgraph so far.
I assigned the TX/RX antenna to the USRP Source and RX2 to the USRP Sink, different frequencies for uplink and downlink…
When I test my flowgraph I can actually see that something is sent on the TX LED and the RX antenna is continuously receiving on the RX side.
I think I would have to connect my RX and TX flowgraphs in some way so that I can be able to transmit and receive at the same time, which doesn’t look to be the case.

Someone would have a working example of an OFDM transceiver so that I see what I miss ?

Below are my TX+RX flowgraph (the separate TX and RX flowgraphs are working autonomously) and the python file I modified in order to integrate the chat aspect at the beginning and end of my flowgraphs.

The GRC:
https://github.com/abeyaert/OFDM_Message_Paging/blob/master/tx_rx_ofdm_b200.grc
Python with chat features :
https://github.com/abeyaert/OFDM_Message_Paging/blob/master/tx_rx_ofdm_b200.py

Any suggestion on them would be appreciated.

Anthony