In today’s programming tutorial, I am going to describe some basics about how we can perform serial port communication from our C#.NET applications. Serial communications can be done via either direct to physical serial port connected to the computer or via a USB to serial converter interface. If the device do require a serial port and your computer don’t have any, you can make use of such converters easily.
This type of communication aren’t as much easy as other similar tasks such as working with logic drive on computer via c# and need use of specific kind of communication protocol.
One interesting thing that you might need to remember that, when the physical serial port are being used, it doesn’t have any PID or VID. But if you are using any specific type of devices which facilitate this kind of communication via USB interface, you can retrieve their PID/VID respectively and communicate accordingly. .NET has a very useful internal classes which can make this kind of communication to be very easy and efficient. Lets have a look into them.
Retrieve List Serial Ports:
OK, lets first see whether we can detect the serial ports from within our application. As a prerequisite, you need to make sure that, while the application is running, the windows user must need to have access to the ports. The following C# code examples will return a list of Serial port names connected to the computer:
public List<string> GetAllPorts()
{
List<String> allPorts = new List<String>();
foreach (String portName in System.IO.Ports.SerialPort.GetPortNames())
{
allPorts.Add(portName);
}
return allPorts;
}
And it is enough for further processing. .NET can understand where to communicate via the port name in string like “COM1”, “COM2” etc.
Using WMI query:
The following code snippet will work similarly as the one given above, but it make use of core WMI and returns a list of Management objects:
private List<ManagementObject> getAllComPort()
{
List<ManagementObject> objct = new List<ManagementObject>();
using (ManagementObjectSearcher searcher = new ManagementObjectSearcher("SELECT * FROM " +
WIN_SERIAL_OBJECT_NAME + ""))
{
foreach (ManagementObject serialPortObj in searcher.Get())
{
objct.Add(serialPortObj);
}
}
return objct;
}
Open Or Close Serial Ports:
well, as have now been able to get the list of ports, now we can start communicating. First step to start serial port communication is to open the port, then send/receive necessary data and finally close the port(s). Lets see an example how we can open and close ports:
System.IO.Ports.SerialPort myPort = new System.IO.Ports.SerialPort("COM1");
if (myPort.IsOpen == false) //if not open, open the port
myPort.Open();
//do your work here
myPort.Close();
Read/Write Data via Serial Port Communication:
OK, now we can start doing the real communication. However, it is very important that, you have prior knowledge what kind of data the connected device is expecting. and you will need to process their response as well to understand what they are saying. For this, you will need the corresponding firmware API command lists. Here, I will give a simple prototype how the send/receive data workflow will be:
using System;
using System.Timers;
public class CommTimer
{
public Timer tmrComm = new Timer();
public bool timedout = false;
public CommTimer()
{
timedout = false;
tmrComm.AutoReset = false;
tmrComm.Enabled = false;
tmrComm.Interval = 1000; //default to 1 second
tmrComm.Elapsed += new ElapsedEventHandler(OnTimedCommEvent);
}
public void OnTimedCommEvent(object source, ElapsedEventArgs e)
{
timedout = true;
tmrComm.Stop();
}
public void Start(double timeoutperiod)
{
tmrComm.Interval = timeoutperiod; //time to time out in milliseconds
tmrComm.Stop();
timedout = false;
tmrComm.Start();
}
}
public void SendReceiveData()
{
byte[] cmdByteArray = new byte[1];
SerialObj.DiscardInBuffer();
SerialObj.DiscardOutBuffer();
//send
cmdByteArray[0] = 0x7a;
SerialObj.Write(cmdByteArray, 0, 1);
CommTimer tmrComm = new CommTimer();
tmrComm.Start(4000);
while ((SerialObj.BytesToRead == 0) && (tmrComm.timedout == false))
{
Application.DoEvents();
}
if (SerialObj.BytesToRead > 0)
{
byte[] inbyte = new byte[1];
SerialObj.Read(inbyte, 0, 1);
if (inbyte.Length > 0)
{
byte value = (byte)inbyte.GetValue(0);
//do other necessary processing you may want.
}
}
tmrComm.tmrComm.Dispose();
SerialObj.DiscardInBuffer();
SerialObj.DiscardOutBuffer();
SerialObj.Close();
}
First thing we are doing here, is discarding existing buffer, if any. Then, we will write an array of bytes to the port. This array can contain several hex values to represent a single command. Here, I have used one . After writing, and before you start reading the response, it’s always good to wait for a while, thus add a slight delay, which helps to make up the time required between receiving and sending reply for the device. In this time, normally, windows do ques your work instruction and sends to devices. But, it may not happen because of CPU scheduling issue etc. So, better to check whether any response came or not. If not, force windows to perform this action now by ‘Application.DoEvents()’ command statement.
References:
For working more with deep communication and troubleshoot, you will need to study carefully the Microsoft’s official documentation on serial object class.
Hope this small tutorial on serial port communication with c# will be helpful to you in some extent. Let me know if you want some more similar tutorials or have any questions. Happy coding :).
Sandip Shinde says
February 21, 2013 at 4:34 amThank You Very Much For This tutorial
I got The New Idea & Concepts To Connect Serial Port
Its Realy HelpFul.
Sandip Shinde
NetSolution Technogies
naseema says
May 13, 2015 at 11:59 pmhow to read com port with using .net?
hussainkhanalfa says
May 19, 2015 at 4:46 pmi need code to read data from atmel 4 pin microcontroller and write data on it again it is on the board
Ramesh KP says
March 15, 2013 at 2:43 ami like this blog, lot of big things described in light manner..!!
Curios User says
March 25, 2013 at 5:28 amMaybe you should write a little bit about the SerialObj and tmrComm, where did they came from ??
Md Ali Ahsan Rana says
March 28, 2013 at 8:40 amHi, thanks for noticing. tmrComm should have been shown to be initialized earlier. It is of type “CommTimer” as given in the code. Also “SerialObj” is of type SerialPort
Phil says
May 7, 2013 at 1:20 pmWere is the CommTimer type found??
Md Ali Ahsan Rana says
May 8, 2013 at 4:45 amHi Phil, I am not sure what is your actually question is. However, there was a small issue in the c# code example as initialization of “tmrComm” variable of type “CommTimer” wasn’t done in proper way. I have modified it. But, if you have something else question, please explain.
Phil says
May 8, 2013 at 4:58 amThanks for the reply, my question is what assembly is “CommTimer” in?
Md Ali Ahsan Rana says
May 8, 2013 at 11:34 amOh yes. I very much appreciate your catch. I thought I did shared it too, but didn’t, just realised after your question. Thanks a lot. I just added that class definition as well. Hope this helps. Please let me know if you still having any issue/have more feedbacks.
Phil says
May 9, 2013 at 11:34 amThanks very much for the additional code, its working now 🙂
aniljacob_75@yahoo.com says
November 2, 2017 at 5:28 amHi Rana,
Do you have a complete code rather than bits and pieces? I am trying to understand how you are calling SendReceiveData. Can you please revert with the entire code please. Unfortunately i am new in C#. Any help will be greatly appreciated.
Thanks
Andargachew Gobena says
May 22, 2013 at 11:44 pmthanks a lot for the tutorial.Can you make a tutorial or guid me to writing device drivers for serial port devices?
Md Ali Ahsan Rana says
May 23, 2013 at 12:45 pmYou mean you want to write driver software for serial port accessible devices? If so, you must need to have the command set that the device accepts and what it replies in response. If you got that, you can even use this article to send and receive data.
Stephan says
September 9, 2013 at 7:38 amWIN_SERIAL_OBJECT_NAME Where is this command form can’t find it sorry I’m a Nube. Is it a Placeholder or a Proper .Net Command
Md Ali Ahsan Rana says
September 30, 2013 at 1:38 pmThat is simply a constant where you will have to mention your target object name. Hope this helps.
xavi says
July 4, 2014 at 4:37 amhere is an alternative explanation, with code and you can download to make tests
ps:if you have only USB ports you can “virtualize” a serial port using the USB port:
– connect with an adapter to de USB port
– install te drivers and select a new created virtualized serial port (in my case COM3)
– uninstall the printer in the control panel printer window (quit device)
– is very important to quit the printer because if not, the port is taken by the printer and when you’re trying to open the port will be an error (“The given port name does not start with COM/com or does not resolve to a valid serial port”)
try it. it works great.
http://msmvps.com/blogs/coad/archive/2005/03/23/SerialPort-_2800_RS_2D00_232-Serial-COM-Port_2900_-in-C_2300_-.NET.aspx%5B^]
Katherine says
August 7, 2014 at 12:44 pmnot helpful, there are a lot of simpler ways to do this
Md Ali Ahsan Rana says
August 7, 2014 at 1:01 pmThere could be, for sure. Why don’t you just share some way/link, I will be happy to share with my readers.
Madan Gehlot says
August 21, 2014 at 3:57 amCan we use serial port communication with AVR micro-controller?
Md Ali Ahsan Rana says
August 21, 2014 at 10:34 amNot sure about that, haven’t tried yet.
sneha says
September 23, 2014 at 3:03 amI am getting error at “Applicatio.DoEvent”. how to resolve it?
I am using WPF
Md Ali Ahsan Rana says
September 23, 2014 at 8:23 amYou can try with this solution, this might help: http://stackoverflow.com/questions/19007288/alternative-to-application-doevents-in-wpf
Sachin says
September 30, 2014 at 6:58 amCan you to get punch in and out data from PunchMachine using above code
ravi says
October 29, 2014 at 2:11 amshowing error::: ‘Timer’ is an ambiguous reference between ‘System.Windows.Forms.Timer’ and ‘System.Timers.Timer’…what to do plz help
bhalaniabhishek says
December 14, 2014 at 3:55 amHow can I send binary file to the GPS device via serial port communication, want to update firmware of device using C#..
can you please reply me I need your help..
Regards,
Abhi
Nizam Khan says
January 13, 2015 at 1:50 amHello Md Ali Ahsan Rana
my problem is that i trying to get input from Weight machine ( Connection= USB, Company=DYMO Endicia Postage Technology,Item No=ES-7500UBLK) in web application in asp.net.Please give me any code if you have for this.
Thanks in advance
Thiha Swe says
January 14, 2015 at 10:29 pmPlease help me . Does it need all ping or which pings need mainly to receive and send data from computer and other device.
zeeshan siddique says
February 3, 2015 at 2:40 amhi . i m working with rfeid serial module , i want to use with it .net apllication i want to know that which approach is better ?
1 : to open serial port when software is running at startup
2: or open serial port when needed after communication close it
please reply .
Md Ali Ahsan Rana says
February 3, 2015 at 11:02 pmIts always wise to make connection on demand(when needed) always without unnecessarily keeping a connection open, unless some exceptional cases.
zeeshan siddique says
February 4, 2015 at 1:24 amthen why sometimes it give error that serial port cannot be opened after several communications ?
siva naidoo says
March 5, 2015 at 7:50 amHi i have a problem with communicating with a serial scale. If i use ReadLine() i get no values, but if i use ReadExisting() i get a constant string for e.g. 40 would show as 40404040404040
How do i get around this?
Sahid Marian says
March 11, 2015 at 4:47 amI have problem, it seems like i have nothing to read, it is always stuck here
while ((SerialObj.BytesToRead == 0) && (tmrComm.timedout == false))
I am using METEX ME 32 prahistoric device, which measures temperature, voltage.. i have been using using USB converter, it’sturned on, and shows value on it’s screen, but program doesnt seen it.
kamran hafeez malik says
May 17, 2015 at 10:28 amaoa . i have a project in which i draw in drawing and same thing is drawn in glcd. through serial communication ,
byte[] buffer_2_send = new byte[1];
byte data_2_send = 0;
data_2_send = Byte.Parse(textBox2.Text);//this way you will get the value 12 in your variable
//we will use a buffer because the serial_port.Write takes either a string or a buffer of data
buffer_2_send[0] = data_2_send;
MessageBox.Show(“” + buffer_2_send + ” ” + buffer_2_send.Length);
serialPort1.Write(buffer_2_send, 0, buffer_2_send.Length);
i basicaly send 12 or like this values on microcontroller
but at recieving side i cant recieve respective value so plz guide me
jimm says
June 24, 2015 at 11:07 pmThank You Great Work
Matt Quinn says
October 3, 2015 at 5:22 pmIf you have an application that writes to a serial port device through a USB adapter, and the application is hard-coded to use COM port 5, is there anything you can do so that moving a laptop that uses this application from one docking station to another will NOT cause Windows Plug and Play to assign a different COM port based on the VID of the second USB-to-serial device being different from the VID of the first USB-to- serial adapter?
The docking stations both use the same peripherals, all plugged into the same USB ports.
The users of these laptops don’t have administrative rights to change the COM port in Device Manager.
Some USB-to-serial adapters advertise ‘COM port retention’, but that only seems to make the laptop use the same COM port for the exact same USB-to-serial adapter (the very same one, not just one that ‘seems’ the same but has a different VID) each time the laptop is connected to that device.
Thanks,
Deep Siddharth Verma says
December 3, 2015 at 5:31 amhey.. i need to communicate with devices that are connected by usb in wpf application… can you please guide me in this.. i am newbie in this..
paul says
March 23, 2016 at 6:15 amwhat assembly is “CommTimer” in?
Gu Hui Quan says
June 12, 2016 at 9:27 pmSystem.IO.Ports.SerialPort myPort = new System.IO.Ports.SerialPort(“COM4”);
if (myPort.IsOpen == false) //if not open, open the port
myPort.Open()
error message:
A device attached to the system is not functioning.
tarun says
September 9, 2016 at 5:01 amthanks i ask you a question i have a software well working in serial port can i use this software over usb port without any change in software
Mohammad says
January 19, 2017 at 1:20 pmHi.excuse me for my bad English!I want to write a program in c# that print papers with Olivetti pr4sl slip printer.but I can’t communicate with this printer and don’t know how to send text directly to this printer in my program.can you help me for this?this printer connected to my pc with COM port and doesn’t have any driver.thanks
Gopakumar says
July 10, 2017 at 4:23 amGood afternoon all,
I need to develop a LIMS(Lab integrated management system) using Asp.net and it should be bidirectional communication that means need to send the data of patient with tests,sample id,date etc to machine and need to get the results back to the computers from machines.Please help me how i can do
Rajesh Maheshwari says
September 16, 2017 at 11:28 pmBy SerialObj.DiscardInBuffer(); you are flushing data in the Serial Port buffer only. Data still remains in the base stream object, which will pop up on reading the port.
So, in addition, do SP.BaseStream.Flush() to really get rid af all existing data
Swati Dewangan says
December 18, 2017 at 6:23 amCan u tell me how to code a program to record the exact time when serial port data arrives in visual studio in C#
Nitin says
April 15, 2019 at 3:10 amI am getting error at “Applicatio.DoEvent”. how to resolve it?