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title How to: Receive Strings From Serial Ports in Visual Basic
ms.custom
ms.date 07/20/2015
ms.prod .net
ms.reviewer
ms.suite
ms.technology
devlang-visual-basic
ms.topic article
helpviewer_keywords
serial ports, retrieving strings
strings [Visual Basic], retrieving from serial ports
My.Resources object
ms.assetid 8371ce2c-e1c7-476b-a86d-9afc2614b6b7
caps.latest.revision 21
author dotnet-bot
ms.author dotnetcontent

How to: Receive Strings From Serial Ports in Visual Basic

This topic describes how to use My.Computer.Ports to receive strings from the computer's serial ports in [!INCLUDEvbprvb].

To receive strings from the serial port

  1. Initialize the return string.

    [!code-vbVbVbalrMyComputer#38]

  2. Determine which serial port should provide the strings. This example assumes it is COM1.

  3. Use the My.Computer.Ports.OpenSerialPort method to obtain a reference to the port. For more information, see xref:Microsoft.VisualBasic.Devices.Ports.OpenSerialPort%2A.

    The Try...Catch...Finally block allows the application to close the serial port even if it generates an exception. All code that manipulates the serial port should appear within this block.

    [!code-vbVbVbalrMyComputer#39]

  4. Create a Do loop for reading lines of text until no more lines are available.

    [!code-vbVbVbalrMyComputer#40]

  5. Use the xref:System.IO.Ports.SerialPort.ReadLine method to read the next available line of text from the serial port.

    [!code-vbVbVbalrMyComputer#41]

  6. Use an If statement to determine if the xref:System.IO.Ports.SerialPort.ReadLine method returns Nothing (which means no more text is available). If it does return Nothing, exit the Do loop.

    [!code-vbVbVbalrMyComputer#42]

  7. Add an Else block to the If statement to handle the case if the string is actually read. The block appends the string from the serial port to the return string.

    [!code-vbVbVbalrMyComputer#43]

  8. Return the string.

    [!code-vbVbVbalrMyComputer#44]

Example

[!code-vbVbVbalrMyComputer#37]

This code example is also available as an IntelliSense code snippet. In the code snippet picker, it is located in Connectivity and Networking. For more information, see Code Snippets.

Compiling the Code

This example assumes the computer is using COM1.

Robust Programming

This example assumes the computer is using COM1. For more flexibility, the code should allow the user to select the desired serial port from a list of available ports. For more information, see How to: Show Available Serial Ports.

This example uses a Try...Catch...Finally block to make sure that the application closes the port and to catch any timeout exceptions. For more information, see Try...Catch...Finally Statement.

See Also

xref:Microsoft.VisualBasic.Devices.Ports
xref:System.IO.Ports.SerialPort?displayProperty=nameWithType
How to: Dial Modems Attached to Serial Ports
How to: Send Strings to Serial Ports
How to: Show Available Serial Ports