How to have multiple connection in TCP client mode ?

[TomElectronic]

Hello,
I am writing FTP client on kinetis MCU with ESP-07S module (ESP8266 integrated).

Wifi connection is working and I can connect (and communicate) with FileZilla server on port 21.
BUT I need to transmit "ASCII data file" to another port WITHOUT disconnected of the actual port (21).

I tried to activate multiple connection with AT+CIPMUX=1 but don't work (link error).

Is it possible to do that ? How ?

Thank you,
best regards from France,
Thomas.

[Her Mary]

Maybe you could try it as:
AT+CIPMUX=1
AT+CIPSTART=0,"your server",port
AT+CIPSTART=1,"another server", another port