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SerialPort Class

Represents a serial port resource.

System.Object
  System.MarshalByRefObject
    System.ComponentModel.Component
      System.IO.Ports.SerialPort

Namespace:  System.IO.Ports
Assembly:  System (in System.dll)
public class SerialPort : Component

The SerialPort type exposes the following members.

  Name Description
Public method SerialPort() Initializes a new instance of the SerialPort class.
Public method SerialPort(IContainer) Initializes a new instance of the SerialPort class using the specified IContainer object.
Public method SerialPort(String) Initializes a new instance of the SerialPort class using the specified port name.
Public method SerialPort(String, Int32) Initializes a new instance of the SerialPort class using the specified port name and baud rate.
Public method SerialPort(String, Int32, Parity) Initializes a new instance of the SerialPort class using the specified port name, baud rate, and parity bit.
Public method SerialPort(String, Int32, Parity, Int32) Initializes a new instance of the SerialPort class using the specified port name, baud rate, parity bit, and data bits.
Public method SerialPort(String, Int32, Parity, Int32, StopBits) Initializes a new instance of the SerialPort class using the specified port name, baud rate, parity bit, data bits, and stop bit.
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  Name Description
Public property BaseStream Gets the underlying Stream object for a SerialPort object.
Public property BaudRate Gets or sets the serial baud rate.
Public property BreakState Gets or sets the break signal state.
Public property BytesToRead Gets the number of bytes of data in the receive buffer.
Public property BytesToWrite Gets the number of bytes of data in the send buffer.
Protected property CanRaiseEvents Gets a value indicating whether the component can raise an event. (Inherited from Component.)
Public property CDHolding Gets the state of the Carrier Detect line for the port.
Public property Container Gets the IContainer that contains the Component. (Inherited from Component.)
Public property CtsHolding Gets the state of the Clear-to-Send line.
Public property DataBits Gets or sets the standard length of data bits per byte.
Protected property DesignMode Gets a value that indicates whether the Component is currently in design mode. (Inherited from Component.)
Public property DiscardNull Gets or sets a value indicating whether null bytes are ignored when transmitted between the port and the receive buffer.
Public property DsrHolding Gets the state of the Data Set Ready (DSR) signal.
Public property DtrEnable Gets or sets a value that enables the Data Terminal Ready (DTR) signal during serial communication.
Public property Encoding Gets or sets the byte encoding for pre- and post-transmission conversion of text.
Protected property Events Gets the list of event handlers that are attached to this Component. (Inherited from Component.)
Public property Handshake Gets or sets the handshaking protocol for serial port transmission of data.
Public property IsOpen Gets a value indicating the open or closed status of the SerialPort object.
Public property NewLine Gets or sets the value used to interpret the end of a call to the ReadLine and WriteLine methods.
Public property Parity Gets or sets the parity-checking protocol.
Public property ParityReplace Gets or sets the byte that replaces invalid bytes in a data stream when a parity error occurs.
Public property PortName Gets or sets the port for communications, including but not limited to all available COM ports.
Public property ReadBufferSize Gets or sets the size of the SerialPort input buffer.
Public property ReadTimeout Gets or sets the number of milliseconds before a time-out occurs when a read operation does not finish.
Public property ReceivedBytesThreshold Gets or sets the number of bytes in the internal input buffer before a DataReceived event occurs.
Public property RtsEnable Gets or sets a value indicating whether the Request to Send (RTS) signal is enabled during serial communication.
Public property Site Gets or sets the ISite of the Component. (Inherited from Component.)
Public property StopBits Gets or sets the standard number of stopbits per byte.
Public property WriteBufferSize Gets or sets the size of the serial port output buffer.
Public property WriteTimeout Gets or sets the number of milliseconds before a time-out occurs when a write operation does not finish.
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  Name Description
Public method Close Closes the port connection, sets the IsOpen property to false, and disposes of the internal Stream object.
Public method CreateObjRef Creates an object that contains all the relevant information required to generate a proxy used to communicate with a remote object. (Inherited from MarshalByRefObject.)
Public method DiscardInBuffer Discards data from the serial driver's receive buffer.
Public method DiscardOutBuffer Discards data from the serial driver's transmit buffer.
Public method Dispose() Releases all resources used by the Component. (Inherited from Component.)
Protected method Dispose(Boolean) Releases the unmanaged resources used by the SerialPort and optionally releases the managed resources. (Overrides Component.Dispose(Boolean).)
Public method Equals(Object) Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected method Finalize Releases unmanaged resources and performs other cleanup operations before the Component is reclaimed by garbage collection. (Inherited from Component.)
Public method GetHashCode Serves as a hash function for a particular type. (Inherited from Object.)
Public method GetLifetimeService Retrieves the current lifetime service object that controls the lifetime policy for this instance. (Inherited from MarshalByRefObject.)
Public method Static member GetPortNames Gets an array of serial port names for the current computer.
Protected method GetService Returns an object that represents a service provided by the Component or by its Container. (Inherited from Component.)
Public method GetType Gets the Type of the current instance. (Inherited from Object.)
Public method InitializeLifetimeService Obtains a lifetime service object to control the lifetime policy for this instance. (Inherited from MarshalByRefObject.)
Protected method MemberwiseClone() Creates a shallow copy of the current Object. (Inherited from Object.)
Protected method MemberwiseClone(Boolean) Creates a shallow copy of the current MarshalByRefObject object. (Inherited from MarshalByRefObject.)
Public method Open Opens a new serial port connection.
Public method Read(Byte[], Int32, Int32) Reads a number of bytes from the SerialPort input buffer and writes those bytes into a byte array at the specified offset.
Public method Read(Char[], Int32, Int32) Reads a number of characters from the SerialPort input buffer and writes them into an array of characters at a given offset.
Public method ReadByte Synchronously reads one byte from the SerialPort input buffer.
Public method ReadChar Synchronously reads one character from the SerialPort input buffer.
Public method ReadExisting Reads all immediately available bytes, based on the encoding, in both the stream and the input buffer of the SerialPort object.
Public method ReadLine Reads up to the NewLine value in the input buffer.
Public method ReadTo Reads a string up to the specified value in the input buffer.
Public method ToString Returns a String containing the name of the Component, if any. This method should not be overridden. (Inherited from Component.)
Public method Write(String) Writes the specified string to the serial port.
Public method Write(Byte[], Int32, Int32) Writes a specified number of bytes to the serial port using data from a buffer.
Public method Write(Char[], Int32, Int32) Writes a specified number of characters to the serial port using data from a buffer.
Public method WriteLine Writes the specified string and the NewLine value to the output buffer.
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  Name Description
Public event DataReceived Represents the method that will handle the data received event of a SerialPort object.
Public event Disposed Occurs when the component is disposed by a call to the Dispose method. (Inherited from Component.)
Public event ErrorReceived Represents the method that handles the error event of a SerialPort object.
Public event PinChanged Represents the method that will handle the serial pin changed event of a SerialPort object.
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  Name Description
Public field Static member InfiniteTimeout Indicates that no time-out should occur.
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Use this class to control a serial port file resource. This class provides synchronous and event-driven I/O, access to pin and break states, and access to serial driver properties. Additionally, the functionality of this class can be wrapped in an internal Stream object, accessible through the BaseStream property, and passed to classes that wrap or use streams.

The SerialPort class supports the following encodings: ASCIIEncoding, UTF8Encoding, UnicodeEncoding, UTF32Encoding, and any encoding defined in mscorlib.dll where the code page is less than 50000 or the code page is 54936. You can use alternate encodings, but you must use the ReadByte or Write method and perform the encoding yourself.

The following code example demonstrates the use of the SerialPort class to allow two users to chat from two separate computers connected by a null modem cable. In this example, the users are prompted for the port settings and a username before chatting. Both computers must be executing the program to achieve full functionality of this example.


using System;
using System.IO.Ports;
using System.Threading;

public class PortChat
{
    static bool _continue;
    static SerialPort _serialPort;

    public static void Main()
    {
        string name;
        string message;
        StringComparer stringComparer = StringComparer.OrdinalIgnoreCase;
        Thread readThread = new Thread(Read);

        // Create a new SerialPort object with default settings.
        _serialPort = new SerialPort();

        // Allow the user to set the appropriate properties.
        _serialPort.PortName = SetPortName(_serialPort.PortName);
        _serialPort.BaudRate = SetPortBaudRate(_serialPort.BaudRate);
        _serialPort.Parity = SetPortParity(_serialPort.Parity);
        _serialPort.DataBits = SetPortDataBits(_serialPort.DataBits);
        _serialPort.StopBits = SetPortStopBits(_serialPort.StopBits);
        _serialPort.Handshake = SetPortHandshake(_serialPort.Handshake);

        // Set the read/write timeouts
        _serialPort.ReadTimeout = 500;
        _serialPort.WriteTimeout = 500;

        _serialPort.Open();
        _continue = true;
        readThread.Start();

        Console.Write("Name: ");
        name = Console.ReadLine();

        Console.WriteLine("Type QUIT to exit");

        while (_continue)
        {
            message = Console.ReadLine();

            if (stringComparer.Equals("quit", message))
            {
                _continue = false;
            }
            else
            {
                _serialPort.WriteLine(
                    String.Format("<{0}>: {1}", name, message) );
            }
        }

        readThread.Join();
        _serialPort.Close();
    }

    public static void Read()
    {
        while (_continue)
        {
            try
            {
                string message = _serialPort.ReadLine();
                Console.WriteLine(message);
            }
            catch (TimeoutException) { }
        }
    }

    public static string SetPortName(string defaultPortName)
    {
        string portName;

        Console.WriteLine("Available Ports:");
        foreach (string s in SerialPort.GetPortNames())
        {
            Console.WriteLine("   {0}", s);
        }

        Console.Write("COM port({0}): ", defaultPortName);
        portName = Console.ReadLine();

        if (portName == "")
        {
            portName = defaultPortName;
        }
        return portName;
    }

    public static int SetPortBaudRate(int defaultPortBaudRate)
    {
        string baudRate;

        Console.Write("Baud Rate({0}): ", defaultPortBaudRate);
        baudRate = Console.ReadLine();

        if (baudRate == "")
        {
            baudRate = defaultPortBaudRate.ToString();
        }

        return int.Parse(baudRate);
    }

    public static Parity SetPortParity(Parity defaultPortParity)
    {
        string parity;

        Console.WriteLine("Available Parity options:");
        foreach (string s in Enum.GetNames(typeof(Parity)))
        {
            Console.WriteLine("   {0}", s);
        }

        Console.Write("Parity({0}):", defaultPortParity.ToString());
        parity = Console.ReadLine();

        if (parity == "")
        {
            parity = defaultPortParity.ToString();
        }

        return (Parity)Enum.Parse(typeof(Parity), parity);
    }

    public static int SetPortDataBits(int defaultPortDataBits)
    {
        string dataBits;

        Console.Write("Data Bits({0}): ", defaultPortDataBits);
        dataBits = Console.ReadLine();

        if (dataBits == "")
        {
            dataBits = defaultPortDataBits.ToString();
        }

        return int.Parse(dataBits);
    }

    public static StopBits SetPortStopBits(StopBits defaultPortStopBits)
    {
        string stopBits;

        Console.WriteLine("Available Stop Bits options:");
        foreach (string s in Enum.GetNames(typeof(StopBits)))
        {
            Console.WriteLine("   {0}", s);
        }

        Console.Write("Stop Bits({0}):", defaultPortStopBits.ToString());
        stopBits = Console.ReadLine();

        if (stopBits == "")
        {
            stopBits = defaultPortStopBits.ToString();
        }

        return (StopBits)Enum.Parse(typeof(StopBits), stopBits);
    }

    public static Handshake SetPortHandshake(Handshake defaultPortHandshake)
    {
        string handshake;

        Console.WriteLine("Available Handshake options:");
        foreach (string s in Enum.GetNames(typeof(Handshake)))
        {
            Console.WriteLine("   {0}", s);
        }

        Console.Write("Handshake({0}):", defaultPortHandshake.ToString());
        handshake = Console.ReadLine();

        if (handshake == "")
        {
            handshake = defaultPortHandshake.ToString();
        }

        return (Handshake)Enum.Parse(typeof(Handshake), handshake);
    }
}


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
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Community Content Add
Annotations FAQ
If the MSDN example doesn't work for you...
It is usually recommended to set DTR and RTS true. If the connected device uses these signals, it will not transmit before the signals are set!
e.g.:
_serialPort.DtrEnable = true;
_serialPort.RtsEnable = true;
No cancelling of noise
I have noticed that when native apps like HyperTerm and Putty open a serial port they cancel the noise that some USB-serial converters generate (like Deltaco). I have used an oscilloscope to verify this. However, when the .Net SerialPort class is used to open a port the noise is not cancelled. The noise prohibits using the .Net SerialPort class to communicate. If I run the same .Net code and configuration on a PC with built in serial port, there is no noise, and the communication works fine.
SerialPort bug regarding fAbortOnError
This class will NOT reset the DCB Flags fAbortOnError flag, which effectively means that any call to Open() in any .NET app will throw an IOException until the machine is restarted.

The only cure to this problem as of now, is to manually clear this bit using P/Invoke as seen in this example:
http://code.mbx.wh01.ipv.no/examples/SerialPortFixer.html (link dead)
http://zachsaw.blogspot.com/2010_07_01_archive.html
Add component in MFC
Hi everyone :) I got a problem with VC2008 or later : How can i add component communication control in MFC (like VC6.0) thanks!

[tfl - 0422 12 11] Hi - and thanks for your post. Community content is not the appropriate place for technical support queries. Instead, you should visit the Technet Forums at http://forums.microsoft.com/technet, where such posts are welcomed and where you stand a much better chance of getting your query resolved. Sorry if that's not the answer you wanted to hear.
Volatile
The _continue variable in the example is used from two different threads. It is a bad practise that should be avoided in the example, or at least done correctly. To make it work on all platforms and in Release configruation, the _continue variable needs to be declared volatile.
Excellent Discussion on Synchronization of the SerialPort class
This thread contains excellent information -- some from a Microsoft developer -- on the internal workings of this class and also on best practices for synchronization and usage of the class.

http://social.msdn.microsoft.com/forums/en-US/netfxbcl/thread/e36193cd-a708-42b3-86b7-adff82b19e5e/
Error C1190
Hi all!,
I ran the example of SerialPort Class and I get the following error:
fatal error C1190: managed targeted code requires a '/clr' option

What do I have to add in the code?

Thanks

Comm64.DLL for x86, x64 and AnyCPU Communications projects
The MS .Net Serial Component is very different from the old MSComm32. If you've got a lot of VB6 code that uses MSComm and you're trying to port it to .Net then why not take a look at Comm64. This is a proper .Net component that, interestingly, uses the same syntax as MSComm32.

As the name suggests, Comm64 is capable of working with native x64 projects but it's also compatible with x86 and AnyCPU projects working in whatever mode your project is targeting.

The fact it uses MSComm32 syntax means it should be quite easy to use in place of MSComm32 when porting applications to .Net

www.comm64.com
Serial Port Application developed using C#.Net

Please find the working exe at the following link. I have tested using virtual comport and its working fine.
http://apachetechnology.net/KC/serialport.aspx