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How to receive more messages from Serial Port c#

I am using System.IO.Ports.
I send messages to device and want to wait for all messages from it.
I am trying do it like this:
message = Console.ReadLine();
_serialPort.Write(message);
Console.WriteLine(_serialPort.ReadExisting());
But it returns only the first line.
I have tried using port.BytesToRead, but I get the same results.
When I use ReadLine() it doesn't return anything.
Edit:
To see all line use Event handler.
Solution for my problem is use \r (enter) on the end line.

ReadExisting return the available bytes available at the exacte time, put a delay befor you read the buffer, a work around would be
message = Console.ReadLine();
_serialPort.Write(message);
Thread.Sleep(200);
Console.WriteLine(_serialPort.ReadExisting());
Edit 2 :
here is how i do it on my projects
private SerialPort port;
string DataReceived = string.Empty;
public string OpenPort(string PortName, int BaudRate)
{
// if the port is already used by other window then return the same instance
if (port != null)
if(port.IsOpen)
return "True";
port = new SerialPort(PortName, BaudRate, Parity.None, 8, StopBits.One);
// Attach a method to be called when there
// is data waiting in the port's buffer
port.DataReceived += new
SerialDataReceivedEventHandler(port_DataReceived);
// Begin communications
try
{
port.Open();
}
catch(Exception ex)
{
return ex.Message;
}
return "True";
}
private void port_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
Thread.sleep(200);
DataReceived = port.ReadExisting();
}
in your main
message = Console.ReadLine();
_serialPort.Write(message);
//use Stopwatch to calculate time befor you can exit from the loop
while(true)
{
if(!string.IsNullOrWhiteSpace(DataReceived))
break;
// Todo : Check stopwatch for timeout
}

Maybe you have a new line issue expected from your serial device try:
message = Console.ReadLine();
_serialPort.WriteLine(message);
Console.WriteLine(_serialPort.ReadExisting()); # try debug here replace with string test = _serialPort.ReadLine();

Serial COM read returns null [duplicate]

I am developing program which need to interact with COM ports.
By learning from this Q&A: .NET SerialPort DataReceived event not firing, I make my code like that.
namespace ConsoleApplication1
{
class Program
{
static SerialPort ComPort;
public static void OnSerialDataReceived(object sender, SerialDataReceivedEventArgs args)
{
string data = ComPort.ReadExisting();
Console.Write(data.Replace("\r", "\n"));
}
static void Main(string[] args)
{
string port = "COM4";
int baud = 9600;
if (args.Length >= 1)
{
port = args[0];
}
if (args.Length >= 2)
{
baud = int.Parse(args[1]);
}
InitializeComPort(port, baud);
string text;
do
{
String[] mystring = System.IO.Ports.SerialPort.GetPortNames();
text = Console.ReadLine();
int STX = 0x2;
int ETX = 0x3;
ComPort.Write(Char.ConvertFromUtf32(STX) + text + Char.ConvertFromUtf32(ETX));
} while (text.ToLower() != "q");
}
private static void InitializeComPort(string port, int baud)
{
ComPort = new SerialPort(port, baud);
ComPort.PortName = port;
ComPort.BaudRate = baud;
ComPort.Parity = Parity.None;
ComPort.StopBits = StopBits.One;
ComPort.DataBits = 8;
ComPort.ReceivedBytesThreshold = 9;
ComPort.RtsEnable = true;
ComPort.DtrEnable = true;
ComPort.Handshake = System.IO.Ports.Handshake.XOnXOff;
ComPort.DataReceived += OnSerialDataReceived;
OpenPort(ComPort);
}
public static void OpenPort(SerialPort ComPort)
{
try
{
if (!ComPort.IsOpen)
{
ComPort.Open();
}
}
catch (Exception e)
{
throw e;
}
}
}
}
My problem is DataReceived event never gets fired.
My program specifications are:
Just .net console programming
I use VSPE from http://www.eterlogic.com
My computer has COM1 and COM2 ports already.
I created COM2 and COM4 by using VSPE.
I get output result from mystring array (COM1, COM2, COM3, COM4)
But I still don't know why DataReceived event is not fired.
Updated
Unfortunately, I still could not make to fire DataReceived event in any way.
So, I created new project by hoping that I will face a way to solve.
At that new project [just console application], I created a class...
public class MyTest
{
public SerialPort SPCOM4;
public MyTest()
{
SPCOM4 = new SerialPort();
if(this.SerialPortOpen(SPCOM4, "4"))
{
this.SendToPort(SPCOM4, "com test...");
}
}
private bool SerialPortOpen(System.IO.Ports.SerialPort objCom, string portName)
{
bool blnOpenStatus = false;
try
{
objCom.PortName = "COM" + portName;
objCom.BaudRate = 9600;
objCom.DataBits = 8;
int SerParity = 2;
int SerStop = 0;
switch (SerParity)
{
case 0:
objCom.Parity = System.IO.Ports.Parity.Even;
break;
case 1:
objCom.Parity = System.IO.Ports.Parity.Odd;
break;
case 2:
objCom.Parity = System.IO.Ports.Parity.None;
break;
case 3:
objCom.Parity = System.IO.Ports.Parity.Mark;
break;
}
switch (SerStop)
{
case 0:
objCom.StopBits = System.IO.Ports.StopBits.One;
break;
case 1:
objCom.StopBits = System.IO.Ports.StopBits.Two;
break;
}
objCom.RtsEnable = false;
objCom.DtrEnable = false;
objCom.Handshake = System.IO.Ports.Handshake.XOnXOff;
objCom.Open();
blnOpenStatus = true;
}
catch (Exception ex)
{
throw ex;
}
return blnOpenStatus;
}
private bool SendToPort(System.IO.Ports.SerialPort objCom, string strText)
{
try
{
int STX = 0x2;
int ETX = 0x3;
if (objCom.IsOpen && strText != "")
{
objCom.Write(Char.ConvertFromUtf32(STX) + strText + Char.ConvertFromUtf32(ETX));
}
}
catch (Exception ex)
{
throw ex;
}
return true;
}
}
I am not sure that I face good luck or bad luck because this new class could make fire DataReceived event which is from older console application that is still running. It is miracle to me which I have no idea how this happen.
Let me tell you more detail so that you could give me suggestion for better way.
Finally I created 2 console projects.
First project is the class which I posted as a question yesterday.
Second project is the class called MyTest which could make fire DataReceived event from First project, at the same time when two of the project is running.
Could anyone give me suggestions on how could I combine these two projects as a single project?

ComPort.Handshake = Handshake.None;
The problem is not that the DataReceived event doesn't fire, the problem is that the serial port isn't receiving any data. There are very, very few serial devices that use no handshaking at all. If you set it to None then the driver won't turn on the DTR (Data Terminal Ready) and RTS (Request To Send) signals. Which a serial port device interprets as "the machine is turned off (DTR)" or "the machine isn't ready to receive data (RTS)". So it won't send anything and your DataReceived event won't fire.
If you really want None then set the DTREnable and RTSEnable properties to true. But it is likely you want HandShake.RequestToSend since the device appears to be paying attention to the handshake signals.
If you still have trouble then use another serial port program like Putty or HyperTerminal to ensure the connection and communication parameters are good and the device is responsive. SysInternals' PortMon utility gives a low-level view of the driver interaction so you can compare good vs bad.

I have never worked with VSPE so I'm not sure if that causes the problem. I have worked with a COM port before and I looked up my code. The only main difference is the way you declare the event. You have:
ComPort.DataReceived += OnSerialDataReceived;
I have it like this:
ComPort.DataReceived += new SerialDataReceivedEventHandler(OnSerialDataReceived);
OnSerialDataReceived is your eventhandler. I'm not sure if this will make any difference, but you can try it. I hope this helps!

I had a quite similar problem. In a graphical application (C# win form) I had a class which encapsulate a SerialPort component. The DataReceived event was firing only one time, but then any following data received didn't fire any event. I solved the problem by calling the Close method in my principal form Closed event function.
No idea of why that changes anything, but now it's working.

Foreach freezing form

I know there are plenty of things about foreach freezing forms but I can't find a solution to my problem. I already have the server portion of this program working I am trying to make a client side that while connecting to the server this code will be preformed txtConn.AppendText("Attempting connection.");
This is the code that I have for the socket connection
private static Socket ConnectSocket(string server, int port, RichTextBox txtConn, BackgroundWorker backgroundWorker1)
{
Socket s = null;
IPHostEntry hostEntry = null;
// Get host related information.
hostEntry = Dns.GetHostEntry(server);
// Loop through the AddressList to obtain the supported AddressFamily. This is to avoid
// an exception that occurs when the host IP Address is not compatible with the address family
// (typical in the IPv6 case).
backgroundWorker1.RunWorkerAsync();
foreach (IPAddress address in hostEntry.AddressList)
{
IPEndPoint ipe = new IPEndPoint(address, port);
Socket tempSocket =
new Socket(address.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
Console.WriteLine(ipe);
try
{
attempt++;
txtConn.Select(txtConn.TextLength, 0);
txtConn.SelectionColor = Color.Aqua;
if (attempt == 1)
{
txtConn.AppendText("Attempting connection.");
}
else if (attempt > 1)
{
txtConn.AppendText("\r" + "Attempting connection.");
}
txtConn.SelectionColor = txtConn.ForeColor;
tempSocket.Connect(ipe);
}
catch (ArgumentNullException ane)
{
Console.WriteLine("ArgumentNullException : {0}", ane.ToString());
txtConn.Select(txtConn.TextLength, 0);
txtConn.SelectionColor = Color.Red;
txtConn.AppendText("\r\n" + "Connection could not be established.");
txtConn.SelectionColor = txtConn.ForeColor;
}
catch (SocketException se)
{
Console.WriteLine("SocketException : {0}", se.ToString());
txtConn.Select(txtConn.TextLength, 0);
txtConn.SelectionColor = Color.Red;
txtConn.AppendText("\r\n" + "Connection could not be established.");
txtConn.SelectionColor = txtConn.ForeColor;
}
catch (Exception e)
{
Console.WriteLine("Unexpected exception : {0}", e.ToString());
txtConn.Select(txtConn.TextLength, 0);
txtConn.SelectionColor = Color.Red;
txtConn.AppendText("\r\n" + "Connection could not be established.");
txtConn.SelectionColor = txtConn.ForeColor;
}
if (tempSocket.Connected)
{
Console.WriteLine("Connected");
s = tempSocket;
break;
}
else
{
continue;
}
}
return s;
}
My program looks like this
When I run the program and connect with say the wrong Port, it checks all the possible ips on my computer and waits till after the foreach statement to display errors or anything. How can I make it actively display this?This is when it runs

You need to run your code in a different thread so that the UI can still update while it is executing.
The easiest way to do this is by adding the connection loop to a new task in the ThreadPool.
ThreadPool.QueueUserWorkItem(i => {
// Connection loop goes here.
});
If you need other options you can also use a Task, BackgroundWorker, etc.

I just answered a similar question here, but to expand on it for your particular case, it looks like you aren't actually using backgroundWorker1. The foreach should be done in a method referenced by the backgroundWorker1.DoWork event. You'll also need to create a method for the backgroundWorker1.ProgressChanged event. You can use ReportProgress to pass a string and then append that message to your textbox:
From your foreach loop in the Worker_DoWork method, you will report progress instead of updating the RichTextBox directly:
worker.ReportProgress(0, "Connection could not be established.");
And then in the Worker_ProgressChanged method, you will use something like this to update the RichTextBox:
txtConn.AppendText(e.UserState.ToString());

Use should use Async methods from Socket class or run this stuff in another thread. You can use BackgroundWorker to do that as well.

Reconnecting to COM after lost connection

I cannot reconnect to COM port after device on the other end abruptly drops connection.
I can connect again only if I close and re-open the application.
Here is my connection function:
public bool connectTurboPump()
{
try
{
if (TPumpSerialPort != null && TPumpSerialPort.IsOpen == true)
return true;
DataRow dr = tblTPump.Rows[0];
Types.Connection TPumpConnection = new Types.Connection();
TPumpConnection.PORT = dr["port"].ToString();
TPumpConnection.BAUD_RATE = Convert.ToInt32(dr["baud"]);
TPumpConnection.PARITY = (Parity)Enum.Parse(typeof(Parity), dr["parity"].ToString(), true);
TPumpConnection.DATA_BITS = Convert.ToInt32(dr["dataBits"]);
TPumpConnection.STOP_BITS = (StopBits)Enum.Parse(typeof(StopBits), dr["stopBits"].ToString(), true);
TPumpConnection.HANDSHAKE = (Handshake)Enum.Parse(typeof(Handshake), dr["handshake"].ToString(), true);
TPumpSerialPort = new SerialPort(TPumpConnection.PORT, TPumpConnection.BAUD_RATE, TPumpConnection.PARITY, TPumpConnection.DATA_BITS, TPumpConnection.STOP_BITS);
TPumpSerialPort.Handshake = TPumpConnection.HANDSHAKE;
TPumpSerialPort.Open();
TPumpSerialPort.NewLine = "\r";
TPumpSerialPort.ReadTimeout = 10000;
TPumpSerialPort.WriteTimeout = 10000;
if (TPumpSerialPort.IsOpen != true)
return false;
return true;
}
catch { return false; }
}
And here is my re-connection function:
public bool reconnectTurboPump(int attempts = 3)
{
try
{
if (TPumpSerialPort != null && TPumpSerialPort.IsOpen == true)
{
TPumpSerialPort.Close();
TPumpSerialPort.Dispose();
}
int i = 1;
while (true)
{
Log(string.Format("Reconnecting Turbo Pump attempt {0}", i));
if (connectTurboPump())
break;
if (i == attempts)
return false;
i++;
}
return true;
}
catch (Exception ex)
{
Log(string.Format("Could not reconnect to Turbo Pump: {0}", ex.Message));
return false;
}
}
Would really appreciate if someone could help.
Thank you.

This doesn't make much sense if this is a true serial port connection. There is no "connected" state, serial ports are very simple devices that have no underlying protocol that establishes a connection.
If this is actually a USB device that emulates a serial port then you'll indeed have this kind of problem. The driver that emulates the serial port invariably gets very sulky when you unplug the USB connector while the port is in use. There actually is a connection protocol for USB devices, the negotiation is done by the driver. They most typically make the port just disappear, this tends to give user code a heart-attack from which it can't recover. Behavior is very unpredictable and varies from one driver to another. There is no cure for this, glue the connector to the port and never assume that unplugging it will solve any problems in your code, even though that's the only thing you can do with USB.

Following Thomas' advice I've changed reconnection script to the following. Now in testing.
public bool reconnectTurboPump(int attempts = 3)
{
try
{
//if (TPumpSerialPort != null && TPumpSerialPort.IsOpen == true)
if (TPumpSerialPort != null)
{
TPumpSerialPort.Close();
TPumpSerialPort.Dispose();
}
int i = 1;
while (true)
{
Log(string.Format("Reconnecting Turbo Pump attempt {0}", i));
Thread.Sleep(2000);
if (connectTurboPump())
break;
if (i == attempts)
return false;
i++;
}
return true;
}
catch (Exception ex)
{
Log(string.Format("Could not reconnect to Turbo Pump: {0}", ex.Message));
return false;
}
}

C# check if a COM (Serial) port is already open

Is there an easy way of programmatically checking if a serial COM port is already open/being used?
Normally I would use:
try
{
// open port
}
catch (Exception ex)
{
// handle the exception
}
However, I would like to programatically check so I can attempt to use another COM port or some such.

I needed something similar some time ago, to search for a device.
I obtained a list of available COM ports and then simply iterated over them, if it didn't throw an exception i tried to communicate with the device. A bit rough but working.
var portNames = SerialPort.GetPortNames();
foreach(var port in portNames) {
//Try for every portName and break on the first working
}

This is how I did it:
[DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
internal static extern SafeFileHandle CreateFile(string lpFileName, int dwDesiredAccess, int dwShareMode, IntPtr securityAttrs, int dwCreationDisposition, int dwFlagsAndAttributes, IntPtr hTemplateFile);
then later on
int dwFlagsAndAttributes = 0x40000000;
var portName = "COM5";
var isValid = SerialPort.GetPortNames().Any(x => string.Compare(x, portName, true) == 0);
if (!isValid)
throw new System.IO.IOException(string.Format("{0} port was not found", portName));
//Borrowed from Microsoft's Serial Port Open Method :)
SafeFileHandle hFile = CreateFile(#"\\.\" + portName, -1073741824, 0, IntPtr.Zero, 3, dwFlagsAndAttributes, IntPtr.Zero);
if (hFile.IsInvalid)
throw new System.IO.IOException(string.Format("{0} port is already open", portName));
hFile.Close();
using (var serialPort = new SerialPort(portName, 115200, Parity.None, 8, StopBits.One))
{
serialPort.Open();
}

For people that cannot use SerialPort.GetPortNames(); because they are not targeting .net framework (like in my case I am using .Net Core and NOT .Net Framework) here is what I ended up doing:
In command prompt if you type mode you get something like this:
mode is an executable located at C:\Windows\System32\mode.com. Just parse the results of that executable with a regex like this:
// Code that answers the question
var proc = new Process
{
StartInfo = new ProcessStartInfo
{
FileName = #"C:\Windows\System32\mode.com",
UseShellExecute = false,
RedirectStandardOutput = true,
CreateNoWindow = true
}
};
proc.Start();
proc.WaitForExit(4000); // wait up to 4 seconds. It usually takes less than a second
// get ports being used
var output = proc.StandardOutput.ReadToEnd();
Now if you want to parse the output this is how I do it:
List<string> comPortsBeingUsed = new List<string>();
Regex.Replace(output, #"(?xi) status [\s\w]+? (COM\d) \b ", regexCapture =>
{
comPortsBeingUsed.Add(regexCapture.Groups[1].Value);
return null;
});
foreach(var item in comPortsBeingUsed)
{
Console.WriteLine($"COM port {item} is in use");
}

I wanted to open the next available port and did it like this.
Please note, is it not for WPF but for Windows Forms.
I populated a combobox with the com ports available.
Then I try to open the first one. If it fails, I select the next available item from the combobox. If the selected index did not change in the end, there were no alternate com ports available and we show a message.
private void GetPortNames()
{
comboBoxComPort.Items.Clear();
foreach (string s in SerialPort.GetPortNames())
{
comboBoxComPort.Items.Add(s);
}
comboBoxComPort.SelectedIndex = 0;
}
private void OpenSerialPort()
{
try
{
serialPort1.PortName = comboBoxComPort.SelectedItem.ToString();
serialPort1.Open();
}
catch (Exception ex)
{
int SelectedIndex = comboBoxComPort.SelectedIndex;
if (comboBoxComPort.SelectedIndex >= comboBoxComPort.Items.Count - 1)
{
comboBoxComPort.SelectedIndex = 0;
}
else
{
comboBoxComPort.SelectedIndex++;
}
if (comboBoxComPort.SelectedIndex == SelectedIndex)
{
buttonOpenClose.Text = "Open Port";
MessageBox.Show("Error accessing port." + Environment.NewLine + ex.Message, "Port Error!!!", MessageBoxButtons.OK);
}
else
{
OpenSerialPort();
}
}
if (serialPort1.IsOpen)
{
StartAsyncSerialReading();
}
}

The SerialPort class has an Open method, which will throw a few exceptions.
The reference above contains detailed examples.
See also, the IsOpen property.
A simple test:
using System;
using System.IO.Ports;
using System.Collections.Generic;
using System.Text;
namespace SerPort1
{
class Program
{
static private SerialPort MyPort;
static void Main(string[] args)
{
MyPort = new SerialPort("COM1");
OpenMyPort();
Console.WriteLine("BaudRate {0}", MyPort.BaudRate);
OpenMyPort();
MyPort.Close();
Console.ReadLine();
}
private static void OpenMyPort()
{
try
{
MyPort.Open();
}
catch (Exception ex)
{
Console.WriteLine("Error opening my port: {0}", ex.Message);
}
}
}
}

Sharing what worked for me (a simple helper method):
private string portName { get; set; } = string.Empty;
/// <summary>
/// Returns SerialPort Port State (Open / Closed)
/// </summary>
/// <returns></returns>
internal bool HasOpenPort()
{
bool portState = false;
if (portName != string.Empty)
{
using (SerialPort serialPort = new SerialPort(portName))
{
foreach (var itm in SerialPort.GetPortNames())
{
if (itm.Contains(serialPort.PortName))
{
if (serialPort.IsOpen) { portState = true; }
else { portState = false; }
}
}
}
}
else { System.Windows.Forms.MessageBox.Show("Error: No Port Specified."); }
return portState;
}
Notes:
- For more advanced technique(s) I recommend using ManagementObjectSearcher Class.
More info Here.
- For Arduino devices I would leave the Port Open.
- Recommend using a Try Catch block if you need to catch exceptions.
- Check also: "TimeoutException"
- More information on how to get SerialPort (Open) Exceptions Here.

public void MobileMessages(string ComNo, string MobileMessage, string MobileNo)
{
if (SerialPort.IsOpen )
SerialPort.Close();
try
{
SerialPort.PortName = ComNo;
SerialPort.BaudRate = 9600;
SerialPort.Parity = Parity.None;
SerialPort.StopBits = StopBits.One;
SerialPort.DataBits = 8;
SerialPort.Handshake = Handshake.RequestToSend;
SerialPort.DtrEnable = true;
SerialPort.RtsEnable = true;
SerialPort.NewLine = Constants.vbCrLf;
string message;
message = MobileMessage;
SerialPort.Open();
if (SerialPort.IsOpen )
{
SerialPort.Write("AT" + Constants.vbCrLf);
SerialPort.Write("AT+CMGF=1" + Constants.vbCrLf);
SerialPort.Write("AT+CMGS=" + Strings.Chr(34) + MobileNo + Strings.Chr(34) + Constants.vbCrLf);
SerialPort.Write(message + Strings.Chr(26));
}
else
("Port not available");
SerialPort.Close();
System.Threading.Thread.Sleep(5000);
}
catch (Exception ex)
{
message.show("The port " + ComNo + " does not exist, change port no ");
}
}

I have been fighting with this problem for a few weeks now. Thanks to the suggestions on here and from the site, https://www.dreamincode.net/forums/topic/91090-c%23-serial-port-unauthorizedaccessexception/ .
I finally came up with a solution that seems to work.
The application I am working on allows a user to connect to a USB device and display data from it.
The Problem I was battling. Along side the application I am writing, I use another serial terminal application for doing my testing. Sometimes I forget to disconnect the COMport being used on the other application. If I do, and try to connect with the application I am writing, I would get an “UnAuthorizedAccessException” error. Along with this exception came some side effects, such as double lines of data being spit out and the application locking up on closing down.
My Solution
Thanks to the advice on here and the other site referenced, this was my solution.
private void checkAndFillPortNameList()
{
SerialPort _testingSerialPort;
AvailablePortNamesFound.Clear();
List<string> availablePortNames = new List<string>();//mySerial.GetAvailablePortNames();
foreach (string portName in SerialPortDataAccess.GetAvailablePortNames())
{
try
{
_testingSerialPort = new SerialPort(portName);
_testingSerialPort.Open();
if (_testingSerialPort.IsOpen)
{
availablePortNames.Add(portName);
_testingSerialPort.Close();
}
}
catch (Exception ex)
{
}
}
availablePortNames.Sort();
AvailablePortNamesFound = new ObservableCollection<string>(availablePortNames);
}
This routine connects to a combobox which holds the available Comports for selection. If a Comport is already, in use by another application, that port name will not appear in the combo box.

You can try folloing code to check whether a port already open or not. I'm assumming you dont know specificaly which port you want to check.
foreach (var portName in Serial.GetPortNames()
{
SerialPort port = new SerialPort(portName);
if (port.IsOpen){
/** do something **/
}
else {
/** do something **/
}
}