Are you sure your device is set up at 19200?
At the end of setup
Serial.write(initPort, sizeof(initPort));
int hexIn = Serial.read();
Where are you sending the initPort?? Is that your device on Serial?? What are you reading back?
In the loop()
uint8_t buffer[128];
uint8_t ind =0;
....
while(buffer[ind-1] != 0x80) // <-- first Time you arrive here what do you think ind-1 is?
Rethink your code structure. The loop should not need a while
If something arrives on serial
handle it and add to buffer at index position
If what I just recieved is the end of the communication
set a '\0' at the end of the buffer
print the buffer
Reset the buffer index to zero
Else increase index and check for buffer end/ overflow
End if
End if