Client:
#if ENABLE_UNET

using UnityEngine.SceneManagement;
using UnityEngine.UI;

namespace UnityEngine.Networking
{
    [RequireComponent(typeof(NetworkManager))]
    [System.ComponentModel.EditorBrowsable(System.ComponentModel.EditorBrowsableState.Never)]
    public class ConnectClient : NetworkBehaviour
    {
        public NetworkLobbyManager manager;
        public string ip = "81.201.63.53";
        public string port = "25565";

        [SyncVar(hook = "OnColorChanged")]
        public Color myColor;

        void Awake()
        {
            manager = GetComponent<NetworkLobbyManager>();
        }

        void OnGUI()
        {
            int xpos = 10;
            int ypos = 40;
            if (!NetworkClient.active && manager.matchMaker == null)
            {
                if (GUI.Button(new Rect(xpos, ypos , 105, 20), "Connect"))
                {
                    manager.networkAddress = ip;
                    manager.networkPort = int.Parse(port);
                    manager.StartClient();
                    SceneManager.LoadScene("server", LoadSceneMode.Additive);
                    SceneManager.SetActiveScene(SceneManager.GetSceneByName("server"));
                }
                ip = GUI.TextField(new Rect(xpos + 115, ypos, 95, 20), ip);
                port = GUI.TextField(new Rect(xpos + 210, ypos, 95, 20), port);
            }
            else
            {
                GUI.Label(new Rect(xpos, ypos + 60, 300, 20), "Client: address=" + manager.networkAddress + " port=" + manager.networkPort);
            }
        }

        void OnColorChanged(Color value)
        {
            myColor = value;
            GameObject.FindWithTag("cube").GetComponent<Renderer>().material.color = myColor;
        }
    }
}
#endif //ENABLE_UNET

Server:

#if ENABLE_UNET

using System.Threading;
using UnityEngine.UI;

namespace UnityEngine.Networking
{
    [RequireComponent(typeof(NetworkManager))]
    [System.ComponentModel.EditorBrowsable(System.ComponentModel.EditorBrowsableState.Never)]
    public class StartHost : NetworkBehaviour
    {
        public NetworkLobbyManager manager;
        public string port = "25565";
        public float countdown = 10.0f;
        public Text gameStartsText;

        [SyncVar(hook = "OnColorChanged")]
        public Color myColor;

        // Runtime variable

        void Awake()
        {
            manager = GetComponent<NetworkLobbyManager>();
        }

        void Update()
        {
            if (NetworkServer.connections.Count >= manager.minPlayers)
            {
                if (countdown >= 0)
                {
                    if (countdown <= 30)
                    {
                        myColor = Color.red;
                        gameStartsText.text = "The game begins in " + countdown.ToString("0") + " seconds";
                    }

                    countdown -= Time.deltaTime;
                }
            }
        }

        void OnGUI()
        {
            int xpos = 10;
            int ypos = 40;

            if (!NetworkServer.active && manager.matchMaker == null)
            {
                if (GUI.Button(new Rect(xpos, ypos, 105, 20), "Start server"))
                {
                    manager.networkPort = int.Parse(port);
                    manager.StartServer();
                }
                port = GUI.TextField(new Rect(xpos + 115, ypos, 95, 20), port);
            }
            else
            {
                GUI.Label(new Rect(xpos, ypos + 30, 300, 20), "Server: port=" + manager.networkPort);
            }

            if (NetworkServer.active)
            {
                if (GUI.Button(new Rect(xpos, ypos, 200, 20), "Stop server"))
                {
                    manager.StopHost();
                }
            }
        }

        void OnColorChanged(Color value)
        {
            myColor = value;
            GameObject.FindWithTag("cube").GetComponent<Renderer>().material.color = myColor;
        }
    }
};
#endif //ENABLE_UNET