Unity - Scripting API:

public function JoinMatch(netId: Networking.Types.NetworkID, matchPassword: string, callback: ResponseDelegate<JoinMatchResponse>): Coroutine;

public function JoinMatch(req: Networking.Match.JoinMatchRequest, callback: ResponseDelegate<JoinMatchResponse>): Coroutine;

Parameters

callback	A callback delegate that takes a JoinMatchResponse that indicates the return of the request after coroutine processing.
req	A JoinMatchRequest describing the match to destroy.
netId	Id of the match to join.
matchPassword	Password to join with.

Coroutine A coroutine for managing the async operation. if using the callback, this can be ignored.

Join a match on the UNET Matchmaker.

This is asynchronous, the callback function will be invoked when the operation completes.