To do a test and check the IP address of the printer. It need to be connected the same sub network as the mobile device. 
The self-test checks whether the printer has any problems. If the printer does not function properly, contact your dealer. The self-test checks the following;

2-1 Make sure paper roll has been installed properly.

2-2 Turn on the power while holding down the FEED button with beep. The self-test begins.

2-3 The self-test prints the current printer status, which provides the control ROM version and the DIP switch setting.

2-4 After printing the current printer status, self-test printing will print the following, and pause (The PAPER LED light blinks). SELF-TEST PRINTING. PLEASE PRESS THE FEED BUTTON.

2-5 Press the FEED button to continue printing. The printer prints a pattern using the built-in character set.

2-6 The self-test automatically ends and cuts the paper after printing the following.


2-7 The printer is ready to receive data as soon as it completes the self-test.