Trouble With Command/Data Multiplex mode

Hello Everybody

I want to use the modem in Multiplex mode and connect to a TCP server. I wrote both the server and client in JAVA. Everything works correctly, I connect to the server and the server can send data back to me, but when I send data to the server (through the modem) the data never reaches the server. I have been struggling with this for a few days now. I don’t know if it’s my packet construction or if I have to send more commands to the modem. As far as I know the modem never transmits the data.

Can Someone Please Help me?

Thank you