Network.Disconnect
static function Disconnect(timeout: int = 200): void;
static void Disconnect(int timeout = 200);
static def Disconnect(timeout as int = 200) as void
Description

Close all open connections and shuts down the network interface.

The timeout parameter indicates how much time in milliseconds the network interface gets to signal to others that it is disconnecting. The network state, like security and password, is also reset.

Note that if you set the timeout to 0 the network interface will shut down before the disconnect notification can be sent to the remote party. For a client this could mean he cannot reconnect to the server as the server thinks he is still connected (after a certain interval the connection will be detected as dropped).
	function OnGUI() {
		if (GUILayout.Button ("Disconnect")) {
			Network.Disconnect();
			MasterServer.UnregisterHost();
		}
	}
using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    void OnGUI() {
        if (GUILayout.Button("Disconnect")) {
            Network.Disconnect();
            MasterServer.UnregisterHost();
        }
    }
}
import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	def OnGUI() as void:
		if GUILayout.Button('Disconnect'):
			Network.Disconnect()
			MasterServer.UnregisterHost()