Search for fnStartTelnet in the utasker project, in the uTasker demo this is in debug.c in the function fnConfigureTelnetServer
The first parameter to fnStartTelnet is the port number.
Telnet_socket = fnStartTelnet(temp_pars->temp_parameters.usTelnetPort, (2*60), 0, 0, fnTELNETListener); // 2 minute inactivity timeout
You can see that the port is pulled from the parameters.
Looking at the Parameter definition in application.c you can see
const PARS cParameters = {
PARAMETER_BLOCK_VERSION, // version number for parameter validity control
(unsigned short)(2*60), // default telnet_timeout - 2 minutes
(CHAR_8 + NO_PARITY + ONE_STOP + USE_XON_OFF + CHAR_MODE), // {43} serial interface settings
23, // TELNET port number
So the port number is defined here, just change this to which ever port you want, I've just changed it to 223 on my test setup and it worked as expected.
Cheers
Martin