SerialPort Class (System.IO.Ports)

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SerialPort Class

Represents a serial port resource.

Inheritance Hierarchy

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

Namespace:  System.IO.Ports
Assembly:  System (in System.dll)
Syntax

Visual Basic
Public Class SerialPort _
	Inherits Component
C#
public class SerialPort : Component
Visual C++
public ref class SerialPort : public Component
F#
type SerialPort =  
    class
        inherit Component
    end

The SerialPort type exposes the following members.

Constructors

  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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Properties

  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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Methods

  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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Events

  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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Fields

  Name Description
Public field Static member InfiniteTimeout Indicates that no time-out should occur.
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Remarks

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.

Examples

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.

Visual Basic

Imports System
Imports System.IO.Ports
Imports System.Threading

Public Class PortChat
    Shared _continue As Boolean
    Shared _serialPort As SerialPort

    Public Shared Sub Main()
        Dim name As String
        Dim message As String
        Dim sComparer As StringComparer = StringComparer.OrdinalIgnoreCase
        Dim readThread As Thread = New Thread(AddressOf 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 sComparer.Equals("quit", message) Then
                _continue = False
            Else
                _serialPort.WriteLine( _
                    String.Format("<{0}>: {1}", name, message))
            End If
        end while

        readThread.Join()
        _serialPort.Close()
    End Sub

    Public Shared Sub Read()
        While (_continue)
            Try
                Dim message As String = _serialPort.ReadLine()
                Console.WriteLine(message)
            Catch ex As TimeoutException
                ' Do nothing
            End Try
        End While
    End Sub

    Public Shared Function SetPortName(ByVal defaultPortName As String) As String
        Dim newPortName As String

        Console.WriteLine("Available Ports:")
        Dim s As String
        For Each s In SerialPort.GetPortNames()
            Console.WriteLine("   {0}", s)
        Next s

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

        If newPortName = "" Then
            newPortName = defaultPortName
        End If
        Return newPortName
    End Function

    Public Shared Function SetPortBaudRate(ByVal defaultPortBaudRate As Integer) As Integer
        Dim newBaudRate As String

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

        If newBaudRate = "" Then
            newBaudRate = defaultPortBaudRate.ToString()
        End If

        Return Integer.Parse(newBaudRate)
    End Function

    Public Shared Function SetPortParity(ByVal defaultPortParity As Parity) As Parity
        Dim newParity As String

        Console.WriteLine("Available Parity options:")
        Dim s As String
        For Each s In [Enum].GetNames(GetType(Parity))
            Console.WriteLine("   {0}", s)
        Next s

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

        If newparity = "" Then
            newparity = defaultPortParity.ToString()
        End If

        Return CType([Enum].Parse(GetType(Parity), newParity), Parity)
    End Function

    Public Shared Function SetPortDataBits(ByVal defaultPortDataBits As Integer) As Integer
        Dim newDataBits As String

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

        If newDataBits = "" Then
            newDataBits = defaultPortDataBits.ToString()
        End If

        Return Integer.Parse(newDataBits)
    End Function

    Public Shared Function SetPortStopBits(ByVal defaultPortStopBits As StopBits) As StopBits
        Dim newStopBits As String

        Console.WriteLine("Available Stop Bits options:")
        Dim s As String
        For Each s In [Enum].GetNames(GetType(StopBits))
            Console.WriteLine("   {0}", s)
        Next s

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

        If newStopBits = "" Then
            newStopBits = defaultPortStopBits.ToString()
        End If

        Return CType([Enum].Parse(GetType(StopBits), newStopBits), StopBits)
    End Function

    Public Shared Function SetPortHandshake(ByVal defaultPortHandshake As Handshake) As Handshake
        Dim newHandshake As String

        Console.WriteLine("Available Handshake options:")
        Dim s As String
        For Each s In [Enum].GetNames(GetType(Handshake))
            Console.WriteLine("   {0}", s)
        Next s

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

        If newHandshake = "" Then
            newHandshake = defaultPortHandshake.ToString()
        End If

        Return CType([Enum].Parse(GetType(Handshake), newHandshake), Handshake)
    End Function
End Class


C#

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);
    }
}


Visual C++

#using <System.dll>

using namespace System;
using namespace System::IO::Ports;
using namespace System::Threading;

public ref class PortChat
{
private:
    static bool _continue;
    static SerialPort^ _serialPort;

public:
    static void Main()
    {
        String^ name;
        String^ message;
        StringComparer^ stringComparer = StringComparer::OrdinalIgnoreCase;
        Thread^ readThread = gcnew Thread(gcnew ThreadStart(PortChat::Read));

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

    static void Read()
    {
        while (_continue)
        {
            try
            {
                String^ message = _serialPort->ReadLine();
                Console::WriteLine(message);
            }
            catch (TimeoutException ^) { }
        }
    }

    static String^ SetPortName(String^ defaultPortName)
    {
        String^ portName;

        Console::WriteLine("Available Ports:");
        for each (String^ s in SerialPort::GetPortNames())
        {
            Console::WriteLine("   {0}", s);
        }

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

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

    static Int32 SetPortBaudRate(Int32 defaultPortBaudRate)
    {
        String^ baudRate;

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

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

        return Int32::Parse(baudRate);
    }

    static Parity SetPortParity(Parity defaultPortParity)
    {
        String^ parity;

        Console::WriteLine("Available Parity options:");
        for each (String^ s in Enum::GetNames(Parity::typeid))
        {
            Console::WriteLine("   {0}", s);
        }

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

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

        return (Parity)Enum::Parse(Parity::typeid, parity);
    }

    static Int32 SetPortDataBits(Int32 defaultPortDataBits)
    {
        String^ dataBits;

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

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

        return Int32::Parse(dataBits);
    }

    static StopBits SetPortStopBits(StopBits defaultPortStopBits)
    {
        String^ stopBits;

        Console::WriteLine("Available Stop Bits options:");
        for each (String^ s in Enum::GetNames(StopBits::typeid))
        {
            Console::WriteLine("   {0}", s);
        }

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

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

        return (StopBits)Enum::Parse(StopBits::typeid, stopBits);
    }

    static Handshake SetPortHandshake(Handshake defaultPortHandshake)
    {
        String^ handshake;

        Console::WriteLine("Available Handshake options:");
        for each (String^ s in Enum::GetNames(Handshake::typeid))
        {
            Console::WriteLine("   {0}", s);
        }

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

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

        return (Handshake)Enum::Parse(Handshake::typeid, handshake);
    }
};

int main()
{
    PortChat::Main();
}


Version Information

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1
.NET Framework Security

Platforms

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.
Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
See Also

Reference