Returns true if your peer type is server.

	function OnGUI() {
		if (Network.isServer)
			GUILayout.Label("Running as a server");
		else if (Network.isClient)
			GUILayout.Label("Running as a client");
	}

using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    void OnGUI() {
        if (Network.isServer)
            GUILayout.Label("Running as a server");
        else
            if (Network.isClient)
                GUILayout.Label("Running as a client");
            
    }
}

import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	def OnGUI() as void:
		if Network.isServer:
			GUILayout.Label('Running as a server')
		elif Network.isClient:
			GUILayout.Label('Running as a client')