SerialPort Class

Represents a serial port resource.

To browse the .NET Framework source code for this type, see the Reference Source.

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

'Declaration
Public Class SerialPort _
	Inherits Component

The SerialPort type exposes the following members.

  NameDescription
Public methodSerialPortInitializes a new instance of the SerialPort class.
Public methodSerialPort(IContainer)Initializes a new instance of the SerialPort class using the specified IContainer object.
Public methodSerialPort(String)Initializes a new instance of the SerialPort class using the specified port name.
Public methodSerialPort(String, Int32)Initializes a new instance of the SerialPort class using the specified port name and baud rate.
Public methodSerialPort(String, Int32, Parity)Initializes a new instance of the SerialPort class using the specified port name, baud rate, and parity bit.
Public methodSerialPort(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 methodSerialPort(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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  NameDescription
Public propertyBaseStreamGets the underlying Stream object for a SerialPort object.
Public propertyBaudRateGets or sets the serial baud rate.
Public propertyBreakStateGets or sets the break signal state.
Public propertyBytesToReadGets the number of bytes of data in the receive buffer.
Public propertyBytesToWriteGets the number of bytes of data in the send buffer.
Protected propertyCanRaiseEventsGets a value indicating whether the component can raise an event. (Inherited from Component.)
Public propertyCDHoldingGets the state of the Carrier Detect line for the port.
Public propertyContainerGets the IContainer that contains the Component. (Inherited from Component.)
Public propertyCtsHoldingGets the state of the Clear-to-Send line.
Public propertyDataBitsGets or sets the standard length of data bits per byte.
Protected propertyDesignModeGets a value that indicates whether the Component is currently in design mode. (Inherited from Component.)
Public propertyDiscardNullGets or sets a value indicating whether null bytes are ignored when transmitted between the port and the receive buffer.
Public propertyDsrHoldingGets the state of the Data Set Ready (DSR) signal.
Public propertyDtrEnableGets or sets a value that enables the Data Terminal Ready (DTR) signal during serial communication.
Public propertyEncodingGets or sets the byte encoding for pre- and post-transmission conversion of text.
Protected propertyEventsGets the list of event handlers that are attached to this Component. (Inherited from Component.)
Public propertyHandshakeGets or sets the handshaking protocol for serial port transmission of data.
Public propertyIsOpenGets a value indicating the open or closed status of the SerialPort object.
Public propertyNewLineGets or sets the value used to interpret the end of a call to the ReadLine and WriteLine methods.
Public propertyParityGets or sets the parity-checking protocol.
Public propertyParityReplaceGets or sets the byte that replaces invalid bytes in a data stream when a parity error occurs.
Public propertyPortNameGets or sets the port for communications, including but not limited to all available COM ports.
Public propertyReadBufferSizeGets or sets the size of the SerialPort input buffer.
Public propertyReadTimeoutGets or sets the number of milliseconds before a time-out occurs when a read operation does not finish.
Public propertyReceivedBytesThresholdGets or sets the number of bytes in the internal input buffer before a DataReceived event occurs.
Public propertyRtsEnableGets or sets a value indicating whether the Request to Send (RTS) signal is enabled during serial communication.
Public propertySiteGets or sets the ISite of the Component. (Inherited from Component.)
Public propertyStopBitsGets or sets the standard number of stopbits per byte.
Public propertyWriteBufferSizeGets or sets the size of the serial port output buffer.
Public propertyWriteTimeoutGets or sets the number of milliseconds before a time-out occurs when a write operation does not finish.
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  NameDescription
Public methodCloseCloses the port connection, sets the IsOpen property to false, and disposes of the internal Stream object.
Public methodCreateObjRefCreates an object that contains all the relevant information required to generate a proxy used to communicate with a remote object. (Inherited from MarshalByRefObject.)
Public methodDiscardInBufferDiscards data from the serial driver's receive buffer.
Public methodDiscardOutBufferDiscards data from the serial driver's transmit buffer.
Public methodDisposeReleases all resources used by the Component. (Inherited from Component.)
Protected methodDispose(Boolean)Releases the unmanaged resources used by the SerialPort and optionally releases the managed resources. (Overrides Component.Dispose(Boolean).)
Public methodEquals(Object)Determines whether the specified object is equal to the current object. (Inherited from Object.)
Protected methodFinalizeReleases unmanaged resources and performs other cleanup operations before the Component is reclaimed by garbage collection. (Inherited from Component.)
Public methodGetHashCodeServes as the default hash function. (Inherited from Object.)
Public methodGetLifetimeServiceRetrieves the current lifetime service object that controls the lifetime policy for this instance. (Inherited from MarshalByRefObject.)
Public methodStatic memberGetPortNamesGets an array of serial port names for the current computer.
Protected methodGetServiceReturns an object that represents a service provided by the Component or by its Container. (Inherited from Component.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodInitializeLifetimeServiceObtains a lifetime service object to control the lifetime policy for this instance. (Inherited from MarshalByRefObject.)
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Protected methodMemberwiseClone(Boolean)Creates a shallow copy of the current MarshalByRefObject object. (Inherited from MarshalByRefObject.)
Public methodOpenOpens a new serial port connection.
Public methodRead(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 methodRead(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 methodReadByteSynchronously reads one byte from the SerialPort input buffer.
Public methodReadCharSynchronously reads one character from the SerialPort input buffer.
Public methodReadExistingReads all immediately available bytes, based on the encoding, in both the stream and the input buffer of the SerialPort object.
Public methodReadLineReads up to the NewLine value in the input buffer.
Public methodReadToReads a string up to the specified value in the input buffer.
Public methodToStringReturns a String containing the name of the Component, if any. This method should not be overridden. (Inherited from Component.)
Public methodWrite(String)Writes the specified string to the serial port.
Public methodWrite(Byte(), Int32, Int32)Writes a specified number of bytes to the serial port using data from a buffer.
Public methodWrite(Char(), Int32, Int32)Writes a specified number of characters to the serial port using data from a buffer.
Public methodWriteLineWrites the specified string and the NewLine value to the output buffer.
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  NameDescription
Public eventDataReceivedRepresents the method that will handle the data received event of a SerialPort object.
Public eventDisposedOccurs when the component is disposed by a call to the Dispose method. (Inherited from Component.)
Public eventErrorReceivedRepresents the method that handles the error event of a SerialPort object.
Public eventPinChangedRepresents the method that will handle the serial pin changed event of a SerialPort object.
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  NameDescription
Public fieldStatic memberInfiniteTimeoutIndicates that no time-out should occur.
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NoteNote

To view the .NET Framework source code for this type, see the Reference Source. You can browse through the source code online, download the reference for offline viewing, and step through the sources (including patches and updates) during debugging; see instructions.

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.

You use the GetPortNames method to retrieve the valid ports for the current computer.

If a SerialPort object becomes blocked during a read operation, do not abort the thread. Instead, either close the base stream or dispose of the SerialPort object.

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.

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 stringComparer__1 As StringComparer = StringComparer.OrdinalIgnoreCase
        Dim readThread As 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 stringComparer__1.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 generatedExceptionName As TimeoutException
            End Try 
        End While 
    End Sub 

    ' Display Port values and prompt user to enter a port. 
    Public Shared Function SetPortName(defaultPortName As String) As String 
        Dim portName As String

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

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

        If portName = "" OrElse Not (portName.ToLower()).StartsWith("com") Then
            portName = defaultPortName
        End If 
        Return portName
    End Function 
    ' Display BaudRate values and prompt user to enter a value. 
    Public Shared Function SetPortBaudRate(defaultPortBaudRate As Integer) As Integer 
        Dim baudRate As String

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

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

        Return Integer.Parse(baudRate)
    End Function 

    ' Display PortParity values and prompt user to enter a value. 
    Public Shared Function SetPortParity(defaultPortParity As Parity) As Parity
        Dim parity As String

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

        Console.Write("Enter Parity value (Default: {0}):", defaultPortParity.ToString(), True)
        parity = Console.ReadLine()

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

        Return CType([Enum].Parse(GetType(Parity), parity, True), Parity)
    End Function 
    ' Display DataBits values and prompt user to enter a value. 
    Public Shared Function SetPortDataBits(defaultPortDataBits As Integer) As Integer 
        Dim dataBits As String

        Console.Write("Enter DataBits value (Default: {0}): ", defaultPortDataBits)
        dataBits = Console.ReadLine()

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

        Return Integer.Parse(dataBits.ToUpperInvariant())
    End Function 
    ' Display StopBits values and prompt user to enter a value. 

    Public Shared Function SetPortStopBits(defaultPortStopBits As StopBits) As StopBits
        Dim stopBits As String

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

        Console.Write("Enter StopBits value (None is not supported and " &
                      vbLf & "raises an ArgumentOutOfRangeException. " &
                      vbLf & " (Default: {0}):", defaultPortStopBits.ToString())
        stopBits = Console.ReadLine()

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

        Return CType([Enum].Parse(GetType(StopBits), stopBits, True), StopBits)
    End Function 
    Public Shared Function SetPortHandshake(defaultPortHandshake As Handshake) As Handshake
        Dim handshake As String

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

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

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

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

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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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