Try creating a new console application with code similar to the following
void Main()
{
using (SerialPort serialPort1 = new SerialPort("COM1"))
using (SerialPort serialPort2 = new SerialPort("COM2"))
{
serialPort1.DataReceived += (sender, args) => {
Console.WriteLine("COM1 Received: " + serialPort1.ReadLine());
};
serialPort2.DataReceived += (sender, args) => {
Console.WriteLine("COM2 Received: " + serialPort2.ReadLine());
};
serialPort1.Open();
serialPort2.Open();
serialPort1.WriteLine("Hello, COM2!");
Thread.Sleep(200);
}
}
The above code opens both serial ports, sets up the data received events, and sends data through it. If you run that code you should see "COM2 Received: Hello, COM2!" output.