Instead of keeping all the print related API calls (connect, beginTransaction, sendData, disconnect) in one method, handle them in separate methods.
As each API call throws its own Epos2Exception, you can go through the below ePOS Sdk documentation link and in Downloaded SDK you can get the sample project.
Also in addition when one device is connected to Printer other devices will get the "Failed to open the device." exception for connect API call, so you will have to implement your own Retry cycle