Hi there. I would like to know if it is possible for me to configure the gateway and the end-devices in a custom frequency differente from that specified in the lorawan specification EU_868? Many thanks in advance 
Not for the first 3 channels, unless you modify the LoRa Server source-code. You could use 5 additional frequencies however (in the LoRaWAN specs, search for CFList). All band config can be found in: https://github.com/brocaar/lorawan/tree/master/band.
Hi, Please I would like to know which part of the LoRa Server source-code can be modified to configure the gateway and the end-devices in a custom frequency ?