How to reproduce:
1. Open attached project
2. Open the "Example" scene
3. Build & Run the project
4. Enter Play mode and select "Lan Host(H)"
5. Open the built project and select "Lan Client(C)"

Actual result: Errors in the editor start appearing and Unity crashes soon.
Expected result: Unity doesn't crash.

Reproducible with: 2017.2.0b5, 2017.1.0p2, 5.6.3f1, 5.6.1f1, 5.6.0a4.
Regression introduced in: 5.6.0a4.
Not reproducible with: 5.6.0a3, 5.6.0a1, 5.5.4p2.

Note: with 5.6.0a3 and older versions only errors "Failed to send multicast: WrongConnection" appears and Unity doesn't crash.

Fixed in: 2017.1.1p2, 2017.2.0b11