Apk made by Unity show this error "Cannot connect to destination host"

Question

I'm trying to post data and get results from the android apk to my own server. Post request is working well on Unity Editor, but it's not working on apk.

Dictionary<string, string> _data = new Dictionary<string, string>();
    _data.Add("from", MenuManager.instance.m_me.m_strOId);
    _data.Add("to", MenuManager.instance.pickedPlayerInfo.m_strOId);
    StartCoroutine(DataController.instance.PostRequest("http://localhost:7000/api/chat", _data, Init));


    public IEnumerator PostRequest(string url, Dictionary<string, string> _param, Action<string> callback)
{
    WWWForm form = new WWWForm();
    if (_param != null)
    {
        foreach (string _key in _param.Keys)
            form.AddField(_key, _param[_key]);
    }
    using (UnityWebRequest webRequest = UnityWebRequest.Post(url, form))
    {
        // Request and wait for the desired page.
        yield return webRequest.SendWebRequest();
        switch (webRequest.result)
        {
            case UnityWebRequest.Result.ConnectionError:
            case UnityWebRequest.Result.DataProcessingError:
                MenuManager.instance.SetLog(": Error: " + webRequest.error);
                break;
            case UnityWebRequest.Result.ProtocolError:
                MenuManager.instance.SetLog(": HTTP Error: " + webRequest.error);
                break;
            case UnityWebRequest.Result.Success:
                MenuManager.instance.SetLog(webRequest.downloadHandler.text);
                callback(webRequest.downloadHandler.text);
                break;
        }
    }
}

Also, I tested this request on postman and it's good. I need your help. Thanks