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SerialPort.ReadTimeout Property

Gets or sets the number of milliseconds before a time-out occurs when a read operation does not finish.

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

[BrowsableAttribute(true)]
public int ReadTimeout { get; set; }

Property Value

Type: System.Int32
The number of milliseconds before a time-out occurs when a read operation does not finish.

ExceptionCondition
IOException

The port is in an invalid state.

- or -

An attempt to set the state of the underlying port failed. For example, the parameters passed from this SerialPort object were invalid.

ArgumentOutOfRangeException

The read time-out value is less than zero and not equal to InfiniteTimeout.

The read time-out value was originally set at 500 milliseconds in the Win32 Communications API. This property allows you to set this value. The time-out can be set to any value greater than zero, or set to InfiniteTimeout, in which case no time-out occurs. InfiniteTimeout is the default.

NoteNote:

Users of the unmanaged COMMTIMEOUTS structure might expect to set the time-out value to zero to suppress time-outs. To suppress time-outs with the ReadTimeout property, however, you must specify InfiniteTimeout.

This property does not affect the BeginRead method of the stream returned by the BaseStream property.

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. This code example is part of a larger code example provided for the SerialPort class.

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) { }
    }
}

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0

.NET Compact Framework

Supported in: 3.5, 2.0

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