// disconnection with server
        private void ToolStripMenuItemDisconnection_Click(object sender, EventArgs e)
        {
            if (client != null && client.Connected())
            {
                toolStripStatusLabel1.BackColor = Color.Red;
                toolStripStatusLabel1.Text      = "Connection with " + client.RemoteEndPoint() + " is broken";

                textBoxTextTransmission.Clear();
                textBoxHashedText.Clear();
                textBoxInformation.Clear();

                InvisibleFields();
                client.Close();
            }
            else
            {
                MessageBox.Show("No connection to the server");
            }
        }
        //connection by host name with server
        private void ToolStripMenuItemByHostName_Click(object sender, EventArgs e)
        {
            FormConnection connection = new FormConnection();

            connection.label1.Text = "Enter name remote host:";
            connection.ShowDialog();

            string hostName = connection.host;

            if (hostName != "")
            {
                try
                {
                    IPHostEntry ipAll = Dns.Resolve(hostName);
                    IPAddress   ip    = ipAll.AddressList[0];

                    client = new Client();
                    client.Connect(ip);

                    if (client.Connected()) // change status label if have connection with server
                    {
                        toolStripStatusLabel1.BackColor = Color.Lime;
                        toolStripStatusLabel1.Text      = "Connected with " + client.EndPoint() + " is established";

                        textButtonTakeTextFromFile.Visible = true;
                        textButtonTransmitInfo.Visible     = true;
                    }
                    else
                    {
                        MessageBox.Show("Enter name or IP-address host", "ERROR");
                    }
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex + "\n\n" + ex.Message);
                }
            }
            else
            {
                MessageBox.Show("Enter name or IP-address host", "ERROR");
            }
        }