[SNMP4J] how to create TCP transport on the preexisting socket?

[Yulia Kozarevska]

Dear all,
I'm trying to implement snmp protocol support for a complex client-server application using snmp4j. I need to create a transport on pre-existing socket. Concerning DefaultUdpTransportMapping class it seems to be easy. I create a new XXXUdpTransportMapping extending DefaultUdpTransportMapping and define a different constructor, creating the socket in a required way:
socket = new XXXSocketFactory().createDatagramSocket(udpAddress.getInetAddress()
        , udpAddress.getPort());

But how to make XXXTcpTransportMapping extending DefaultTcpTransportMapping to behave similarly (work on already existing socket)?
Thank you very much in advance.
Best regards,
Julia