https://devzone.nordicsemi.com/f/nordic-q-a/8302/best-service-choise-for-packet-exchange-between-2-nrf51822Hello, I have 2 nRF51822 with S130. One is central, the other is device. I want to exchange custom data between these 2 devices after connection. What is service best choise ? (i want datagrams like UDP but with acknowledgement). Can both sidesen-USTelligent Community 13Tue, 21 Jul 2015 21:48:52 GMThttps://devzone.nordicsemi.com/thread/29981?ContentTypeID=1Tue, 21 Jul 2015 21:48:52 GMT137ad170-7792-4731-bb38-c0d22fbe4515:d88b23e7-eb32-421c-9eb7-8311ed0dd15aPetter Myhre<p>I&#39;m sorry, I wasn&#39;t sure what kind of services you were talking about. The GATT server needs to have services and characteristics to be able to transfer data. If you have a custom service you should use a 128-bit UUID for it, just like the NUS service is doing. I&#39;m not sure what you mean by what service is the best choice, you just make one, with characteristics that suits your requirements.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/29980?ContentTypeID=1Tue, 21 Jul 2015 20:04:19 GMT137ad170-7792-4731-bb38-c0d22fbe4515:015e4b2d-f4e8-4264-874e-288eb5d2b01cFabien Comte<p>Thank you for the response. I imagined that you must use services on GATT (like NUS) but you say that it&#39;s not mandatory and i can use raw GATT, right ?</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/29979?ContentTypeID=1Tue, 21 Jul 2015 12:08:35 GMT137ad170-7792-4731-bb38-c0d22fbe4515:5baa57e0-133a-45b7-a45f-d670aec57cf0Petter Myhre<p>You use GATT to transfer data. The peripheral (&quot;device&quot;) is usually a GATT server and the central is usally a GATT client.</p> <p>Both can initate a transfer, and all transfers are acked in the link layer. The client can transfer data to the server by writing to it. The client can also read data on the server.</p> <p>The server can transfer data by sending notifications and indications to the client.</p><div style="clear:both;"></div>