Why do i get this error in my muiltiplayer Game

This is my code below

using UnityEngine;
using System.Collections;
using UnityEngine.Networking;
using UnityEngine.UI;

public class NetworkManager_Custom : NetworkManager {


    public void StartupHost()
    {
        SetPort();
        NetworkManager.singleton.StartHost();
    }

    public void JoinGame()
    {
        SetIPAddress();
        SetPort();
        NetworkManager.singleton.StartClient();
    }

    void SetIPAddress()
    {
        string ipAddress = GameObject.Find("InputFieldIPAddress").transform.FindChild("Text").GetComponent<Text>().text;
        NetworkManager.singleton.networkAddress = ipAddress;
    }

    void SetPort()
    {
        NetworkManager.singleton.networkPort = 7777;
    }

    void OnLevelWasLoaded(int level)
    {
        if (level == 0)
        {
            //SetupMenuSceneButtons();
            StartCoroutine(SetupMenuSceneButtons());
        }

        else
        {
            SetupOtherSceneButtons();
        }
    }

    IEnumerator SetupMenuSceneButtons()
    {
        yield return new WaitForSeconds(0.3f);
        GameObject.Find("ButtonStartHost").GetComponent<Button>().onClick.RemoveAllListeners();
        GameObject.Find("ButtonStartHost").GetComponent<Button>().onClick.AddListener(StartupHost);

        GameObject.Find("ButtonJoinGame").GetComponent<Button>().onClick.RemoveAllListeners();
        GameObject.Find("ButtonJoinGame").GetComponent<Button>().onClick.AddListener(JoinGame);
    }

    void SetupOtherSceneButtons()
    {
        GameObject.Find("ButtonDisconnect").GetComponent<Button>().onClick.RemoveAllListeners();
        GameObject.Find("ButtonDisconnect").GetComponent<Button>().onClick.AddListener(NetworkManager.singleton.StopHost);
    }


}

and this is the error that i get

Cannot open socket on ip {*} and port {7777}; check please your network, most probably port has been already occupied
UnityEngine.Networking.NetworkManager:StartHost()
NetworkManager_Custom:StartupHost() (at Assets/Scripts/Networking/NetworkManager_Custom.cs:12)
UnityEngine.EventSystems.EventSystem:Update()

all help is appreciated

I had the same problem, just add NetworkServer.Reset(); before NetworkManager.singleton.StartHost();.

Cheers! @IrishBruse

i know that error is when you try to create other server but you already have created 1 with the same port. Does anybody know how to capture this error?