About ATT_MTU

[Stayhungry]

According to BLUETOOTH SPECIFICATION Version 5.0 | Vol 3, Part G page 2248

Exchange MTU procedure is initiated by the Cilent, and only be initiated once.

But by looking at the data_length_update function in nrf_ble_gatt.c, Exchange MTU is initiated regardless of whether the device is a server or a client

According to the sniffer made with PCA10040, found both client and server initiated an Exchange MTU procedure, is this a violation of the rules?

My client is iphone6s, use APP is LightBlue, but I think APP is not the key.

[run_ar]

Not sure exactly which softdevice you are using, but the SD supports both server and client role, so this could happen. Note that on page 2185, you can see that "It is permitted, (but not necessary - see 2.) to exchange MTU in both directions, but the MTUs shall be the same in each direction (see 1.)

[Stayhungry]

Thanks.Your idea is to suppose that softdevice supports both client and server, so that each of these initiating exchange MTUs is permissible? I have a hypothetical question, if the softdevice only supports server does not support the client, is not it can not initiate exchange MTU?