SerialDataReceivedEventHandler is not firing

我正在尝试使用c#编写从串行端口接收的代码。

我使用VSPC实用程序从两个端口COM27和COM28生成桥当我写COM27发送数据到COM28，我可以看到它使用Putty连接，但是当我试图使用以下代码制作程序时，它不起作用，SerialDataReceivedEventHandler没有触发。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO.Ports;
using System.Threading;
using System.Diagnostics;
namespace csh_serial2_pic
{
public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }
    //
    private void button1_Click(object sender, EventArgs e)
    {
        string[] ports = SerialPort.GetPortNames();
        foreach (string port in ports)
        {
            comboBox1.Items.Add(port);
        }
    }
    //
    string t;
    private void button2_Click(object sender, EventArgs e)
    {
        t = comboBox1.Text.ToString();
        sErial(t);
    }
    // Method
    SerialPort sp;
    void sErial(string Port_name)
    {
        //ThreadPool.SetMinThreads(2, 4); 
        sp = new SerialPort(Port_name, 9600, Parity.None, 8, StopBits.One);
        sp.ReadTimeout = 1000;
        sp.WriteTimeout = 1000;
        sp.ReadBufferSize = 4096;
        sp.ReceivedBytesThreshold = 1;
        //
        sp.DataReceived += new SerialDataReceivedEventHandler(DataReceivedHandeler);
        sp.Open();
        sp.DtrEnable = true;
        sp.RtsEnable = true;
        //System.Threading.Thread.Sleep(10);
        //sp.Close();

    }
    //
    private void DataReceivedHandeler(object sender, SerialDataReceivedEventArgs e)
    {
        SerialPort sp = (SerialPort)sender ;
        Debug.Print("receiving!");
        string data = sp.ReadExisting();
        Console.WriteLine("received: " + data);
        Debug.Print(data);
        string w = sp.ReadLine();
        if (w != string.Empty)
        { 
            Invoke(new Action (() => richTextBox1.AppendText(w)));
        }
    }
}
}

所以谁都可以帮我解决这个问题