Windows Standard
Serial Communications
for Visual Basic
Programmer's Manual
(WSC_4VB)
Version 4.3
September 27, 2007
This software is provided as-is.
There are no warranties, expressed or implied.
Copyright (C) 2007
All rights reserved
MarshallSoft Computing, Inc.
Post Office Box 4543
Huntsville AL 35815
Voice : 1.256.881.4630
email : info@marshallsoft.com
Web : www.marshallsoft.com
MARSHALLSOFT is a registered trademark of MarshallSoft Computing.
1 Introduction
1.1 Features2 Library Overview
1.2 Documentation Set
1.3 Example Program
1.4 Installation
1.5 Uninstalling
1.6 Pricing
1.7 Updates
2.1 Dynamic Link Libraries3 Compiler Issues
2.2 Keycode (License Key)
2.3 Dynamic Strings
2.4 Limitations on COM Ports
2.5 Win32 STDCALL and DECLSPEC
2.6 Waiting for New Serial Data
2.7 Using Threads
2.8 WSC Class
2.9 Using VB.Net
2.10 VBA Applications
2.11 PowerBuilder
2.12 Adding WSC4VB To A Project
2.13 Error Display
2.14 SioEvent Logic
2.15 Virtual Serial Ports
2.16 Using 16-bit Visual Basic
2.17 Visual Basic Problems
3.1 Visual Basic Makefiles4 VB 3/4/5/6 Example Programs
3.2 Compiling Example Programs
3.3 Compiling WSC
4.1 WSCVER5 VB.Net Example Programs
4.2 EASY
4.3 SELFTEST
4.4 MODEM
4.5 TERM
4.6 FINDER
4.7 ATOK
4.8 DEVICE
4.9 MESSAGE
4.10 XMS, XMR, YMS, & YMR
4.11 PUTTYPE
5.1 WSCVER.VB6 Revision History
5.2 EASY.VB
5.3 SELFTEST.VB
5.4 XMS.VB & XMR.VB
The Windows Std Serial Communications Library (WSC4VB) is a component library of functions providing the capability to quickly write serial communication applications in Visual Basic or VB.NET. The WSC component library uses the standard Windows API (Application Programmer's Interface) to communicate with any device connected to a serial port.
A straight forward interface is provided to access data from a serial port using RS232 or multi-drop RS422 or RS485 ports. WSC also supports virtual serial ports using Bluetooth serial and USB to serial converters
Windows Std Serial Communications Library (WSC4VB) includes 20 VB and VB.NET example programs demonstrating serial communication functions that have been tested on multiple computers running Windows 95/98, Windows Me, Windows NT4, Windows 2000, Windows Vista and Windows XP. The WSC4VB library supports and has been tested with several Visual Basic compilers, from VB 3.0 through VB 6.0 and VB.Net. WSC can also be used with any VBA (Visual Basic for Applications) language such as Excel, Access, MS Office, etc.
Both Win16 and Win32 DLLs are provided. The WSC DLL's (WSC16.DLL and WSC32.DLL) can be used from any language (C/C++, Visual C++ .NET, ,NET, Visual C#, Visual FoxPro, Delphi (Delphi .NET), Visual FoxPro, Visual dBase, and Xbase++) capable of calling the Windows API.
MarshallSoft provides separate products for WIN/CE for eVB (WSC4eVB) and for eVC (WSC4eVC). Evaluation versions for each serial communication library may be downloaded from our web site at
http://www.marshallsoft.com/serial-communication-library.htm
Our goal is to provide a robust serial communication library component that you and your customers can depend upon. A fully functional evaluation version is available. Contact us if you have any questions.
When comparing the Windows Standard Serial Communications Library against our competition, note that:
MarshallSoft also has versions of the Windows Standard Serial Communications Library for Visual C/C++ (WSC4C), Delphi (WSC4D), PowerBASIC (WSC4PB), Visual FoxPro (WSC4FP), Visual dBASE (WSC4DB), and Xbase++ (WSC4XB). All versions of WSC use the same DLLs (WSC16.DLL or WSC32.DLL). However, the examples provided for each version are written in the specified computer environment. Development time is shortened because programmers need only learn one interface.
The latest versions of the Windows Standard Serial Communications Library (WSC) can be downloaded from our web site at http://www.marshallsoft.com/serial-communication-library.htm
Some of the many features of the Windows Serial Communications Library for Visual Basic (WSC4VB) are:
A good selection of Visual Basic (and VB.Net) example programs with full source code is included. Refer to Section 5 for more details on each of the example programs.
WSCVER : Program that displays the WSC version number.
EASY : A simple terminal emulator program.
SELFTEST : Performs COM port functionality testing.
MODEM : Same as EASY but controls flow control, modem lines, etc.
TERM : Terminal emulator with XMODEM, YMODEM, and ANSI support.
FINDER : Finds a modem connected to one of the serial ports.
ATOK : Sends "AT" to modem, uses WSC class (WscClass.cls).
DEVICE : Sends text string to serial device.
MESSAGE : Send Windows message when incoming bytes are detected.
XMS/XMR : XMODEM Send & XMODEM Receive programs.
YMS/YMR : YMODEM Send & YMODEM Receive programs.
PUTTYPE : Transmits user defined data type.
VERSION.VB VB.Net version of the WSC version program (WSCVER).
EASY.VB VB.Net version of the simple terminal program (EASY).
SELFTEST.VB VB.Net version of the COM port functionality program (SELFTEST).
XMS.VB VB.Net version of the XMODEM Send program (XMS).
XMR.VB VB.Net version of the XMODEM Receive program (XMR).
The complete set of documentation consists of four manuals in three formats. This is the first manual (WSC_4VB) in the set.
The WSC_4VB Programmer's Manual is the language specific (Visual Basic and VB.NET) manual. All language dependent programming issues are discussed in this manual. Information needed to compile your programs in a VB environment is provided in this manual.
The WSC User's Manual (WSC_USR) discusses language independent serial communications programming issues including modem control. Purchasing and license information is also provided.
The WSC Reference Manual (WSC_REF) contains details on each individual WSC function.
The Serial Communications User's Manual (SERIAL) contains background information on serial port hardware.
Each manual comes in three formats:
The documentation is also provided on our web site at
http://www.marshallsoft.com/wsc4vb.htm
The following example program segment sets DTR (Data Terminal Ready).
' pass the keycode (0 for evaluation version)
Code = SioKeyCode(WSC_KEY_CODE)
' open port COM1
Code = SioReset(COM1, 512, 512)
If Code < 0 Then
' process error
Call SayError(EXAMPLE, Code)
Call ShutDown
Exit Sub
End If
' set DTR
Code = SioDTR(COM1, ASC("S"))
Refer to section 5.0 for complete examples with source.
WSC4VB comes configured for 32-bit Visual Basic (VB4 and above). Before compiling for 16-bit Visual Basic (VB3 & 16-bit VB4), you must first run READY16.BAT in the APPS directory as described in Section 3.5.
Uninstalling WSC4VB is very easy. WSC4VB does NOT modify the registry. First, delete the WSC4VB project directory created when installing WSC4VB. Second, delete WSC16.DLL and WSC32.DLL from your Windows directory, typically C:\WINDOWS for Windows 95/98/Me/XP or C:\WINNT for Windows NT/2000.
A developer license for WSC4VBcan be registered for $115 (or $195 with ANSI C source code to the library DLL's). Purchasing details can be found in Section 1.3 "How to Purchase" in the WSC User's Manual (WSC_USR.HTM). Also see INVOICE.TXT provided with the evaluation person or order directly on our web site at
http://www.marshallsoft.com/order.htm
When a developer license is purchased for WSC4VB, the developer will received a new a set of registered DLLs plus a license file (WSCxxxx.LIC). The license file is needed to download updates to the registered DLL's for a period of one year from purchase. Updates can be downloaded from
http://www.marshallsoft.com/oem.htm
After one year, your license must be updated if you want to be able to download updates. Your license can be updated for :
If source code was previously purchased, updates to the source code can be purchased for $50 along with the DLL update. Note that the registered DLL's never expire.
The Windows Standard Serial Communications Library (WSC) has been tested on multiple computers running Windows 95/98/Me/XP/Vista, and Windows NT/2000.
The WSC4VB library has also been tested with several Visual Basic compilers, from VB 3.0 through VB 6.0 and VB.Net. WSC can also be used with any VBA language such as Excel, Access, MS Office as well as PowerBuilder.
The WSC4VB serial communication library component includes both Win16 and Win32 dynamic link libraries (DLL). A DLL is characterized by the fact that it need not be loaded until required by an application program and that only one copy of the DLL is necessary regardless of the number of application programs that use it. Contrast this to the traditional static library that is bound to each and every application that uses it at link time.
An important advantage that DLLs have over other "popular" library formats such as VBX or OCX is that DLLs are callable by all Windows applications. Since DLLs are the building blocks of the Windows Operating System, they will not be replaced by a "newer technology".
WSC16.DLL and WSC32.DLL each has a keycode encoded within them. Your keycode is a 9 or 10 digit decimal number (unless it is 0), and will be found in the file KEYCODE.BAS and KEYCODE.VB. The keycode for the evaluation (shareware) version is 0. You will receive a new keycode and a set of new DLL's when registering. The KEYCODE is passed to SioKeyCode.
If you get an error message (value -108) when calling SioKeyCode, it means that the keycode in your application does not match the keycode in the DLL. After registering, it is best to remove the evaluation version of the WSC32.DLL and WSC16.DLL from the Windows search path or delete them.
The Visual Basic language uses a technique known as "garbage collection" to manage string space at runtime and may be called internally at any time by the Visual Basic runtime, asynchronous to what you may be doing in your code.
When passing a string buffer to a DLL function into which text will be copied, it is strongly recommended that the local string be allocated immediately before use. For example, a string buffer is passed to the user defined dllGetMessage function , which copies a text message into it. Note that SPACE$(80) is called immediately before dllGetMessage.
Dim Code As Integer
Dim Buffer As String * 80
' allocate buffer just before call to dllGetMessage
Buffer = SPACE$(80)
' copy message into 'Buffer'
Code = dllGetMessage(Buffer, 80)
' message text is now in 'Buffer'
This technique is not necessary for passing a string to a DLL function, only when passing a buffer to a DLL into which data is to be placed by the DLL function.
The 32-bit version of WSC4VB (WSC32.DLL) can use any port from COM1 to COM256, provided that the port is known to Windows 95/98/NT/2000/Me/XP/Vista and there is physical hardware present.
WSC32 is written in ANSI C and is compiled using the _stdcall and _declspec keywords. This means that WSC4VB uses the same calling conventions and file naming conventions as the Win32 API. In particular, function names are NOT decorated. There are neither leading underscores nor trailing "@size" strings added to function names.
The WSC32.DLL functions may be called by any Windows application program capable of calling the Windows API provided the proper declaration file is used.
All serial data is moved from the UART's buffer to the receive queue in memory (by the Windows serial port driver) under interrupt control. Similarly, all out going serial data is moved to the transmit queue in memory.
There are several methods that can be used to wait for new incoming serial data, as follows:
The most straightforward method is to use a VB timer to check every so often. The timer interval should be set between 50 milliseconds and 250 milliseconds. Setting it much less than 50 milliseconds would consume considerable system resources polling, and setting it greater than 250 milliseconds will result in sluggish menu response times. A good compromise is to set the timer interval to 125 milliseconds.
The "Message Method" is probably the most natural method to use with Visual Basic (recall that WSC works with many different computer languages). In this method, the SioMessage function is called which sends a Windows message to a VB button when new data is ready to be read.
This method uses SioEvent in a thread (background process) which blocks (efficiently waits) until new data is available. This method requires creating a thread in VB. However, although it is possible to create a thread in VB5, it is not recommended since VB5 is not thread safe.
This method uses the SioEventWait function in a timer procedure to block (efficiently wait) until new data is available or until the timer period expires. A good choice for the timer interval is 250 milliseconds because it allows quick response to user input and also at the same time minimizes polling. Note that a 250 millisecond interval represents quite a large interval of CPU time.
The Windows Standard Serial Communications Library for Visual Basic (WSC4VB) is thread safe, and can be used from any Windows application capable of using threads.
The "AddressOf" operator, which was added to Visual Basic beginning in version 5.0, is required in order to create and run Win32 threads in Visual Basic 5.
The necessary Win32 thread functions are declared in the file SYSTEM32.BAS.
The WSC class "wscClass" (wscClass.cls) is a Visual Basic class wrapper for making calls to WSC32.DLL. The class name for each function is the same as the DLL function, except the leading "wsc" is replaced by "f".
Those functions that return strings do so by use of the "String Result" property. Instantiate wscClass as any other class in VB:
Dim X As New wscClass
Classes were added to Visual Basic beginning with version 5.0, and are required in order to compile wscClass. Refer to the ATOK example project for an example of using wscClass
There are a few differences between VB 4/5/6 and VB.NET that affect writing programs that use WSC.
Buffer = Space(80) ' allocate memory for "Buffer"
Code = SioWinError(Buffer, 80)
WSC can be used with Microsoft VBA (Visual Basic for Applications) applications such as EXCEL, ACCESS, and Microsoft Office. Note that WSC16.DLL must be used for 16-bit applications, even if running under Windows 95/98/Me or NT/2000. See the file VBA32.TXTas well as EXCEL.TXT, ACCESS.TXT and WORD.TXT in the DOCS directory for more information.
WSC can also be used with Power Builder applications. See PBUILDER.TXT for more information.
WSC.PBI : Power Builder declaration file.
Copy WSC16.BAS (if running VB 3.0 or 16-bit VB 4.0), WSC32.BAS (if running VB 4/5/6), or WSC32.VB (if running VB.Net) to the same directory (folder) as the application program to which you want to add WSC code. You will find these files in the APPS directory (folder) created when you ran SETUP, usually C:\WSC4VB\APPS.
Open your existing project with "File", "Open Project". Then choose "File", "Add File", then add WSC16.BAS and KEYCODE.BAS to your project. WSC functions can now be called from your Visual Basic program.
Open your existing project with "File", "Open Project". Then choose "Insert", "Module", then add WSC32.BAS and KEYCODE.BAS to your project. If prompted to add "DAO 2.50 Object Library", choose "no". WSC functions can now be called from your VB program.
Open your existing project with "File", "Open Project". Then choose "Project", "Add Module", then add WSC32.VB and KEYCODE.VB to your project. WSC functions can now be called from your VB.NET program.
The error message text associated with WSC error codes can be displayed by calling SioError (refer to sioerror.c and paint.c) in GUI mode applications or SayError (see SayError.c) in console mode applications. Each sample program contains examples of error processing.
SioEvent, SioEventChar, and SioEventWait will block until the specified event occurs. If a call to SioEvent, SioEventChar, or SioEventWait is placed in a thread, then the thread will block but the application calling the thread will not.
See the Event.c, EventChar.c, and EventWait.c example programs.
A "virtual" serial port is COM port that appears to be a real RS232 serial port to the Windows API (and thus to WSC), but is in reality a COM port emulator.
The two most common virtual ports are those created for USB/serial port converters and Blue Tooth. WSC will work with most USB to serial port converts and with Bluetooth serial.
More information about Virtual serial ports can be found in Section 2.12 of the WSC User's Manual (WSC_USR). (http://www.marshallsoft.com/wsc_usr.htm#Section_2.12 )
WSC4VB comes configured for 32-bit Visual Basic (32-bit VB4 and up). Before compiling for 16-bit Visual Basic (VB3 & 16-bit VB4), you must run READY16.BAT in the APPS directory, which performs the following copies:
COPY WSC16.BAS WSC4VB.BAS
COPY XYM16.BAS XYM.BAS
COPY ASD16.BAS ASD.BAS
COPY MIO16.BAS MIO.BAS
COPY ERRORS16.BAS ERRORS.BAS
There is also a READY32.BAT to copy 32-bit versions of the above, although WSC4VB is already configured for 32-bit Visual Basic.
If you terminate your program when running inside the Visual Basic environment, and you do not call SioDone first, you will leave VB itself with an open handle to your COM port. When you run again, you will get an "ACCESS DENIED" error and you must re-start VB itself.
Also refer to Section 7 "Resolving Problems" in the User's Manual (WSC_USR.DOC, WSC_USR.HTM or online at http://www.marshallsoft.com/wsc_usr.htm#Section_7).
The Windows Serial Communications Library for Visual Basic component library supports and has been tested with all versions of Microsoft Visual Basic (VB3, VB 4, VB 5, VB 6 and VB.NET).
The first Visual Basic for Windows (version 3.0) uses a text file known as a "Visual Basic makefile" (.MAK) to list all the file components necessary to compile a program. Beginning in version 4.0, the "Visual Basic Project file" (.VBP) was added. Both formats are "project files".
Visual Basic MAK files are provided with most example programs. Most example source code is saved in Visual Basic 3.0 format so that it can be read by all versions of Visual Basic.
Visual Basic project files (*.VBP) are provided for example programs that require VB 5.0 or 6.0. The example programs can be compiled from the Visual Basic development environment using the provided Visual Basic makefiles. Choose "File", then "Open Project" from the main VB menu.
The example program code is stored in VB 3.0 (WIN16) and VB 4.0 (WIN32) formats. All 16-bit project files end in "16.MAK" (e.g.: WSCVER16.MAK) while 32-bit project files end with "32.VBP" (e.g.: WSCVER32.VBP). All 32-bit versions of VB (VB4 and above) can open files stored in VB4 format.
When saving the example programs in VB version 5.0 or VB 6.0 format, answer "no" if asked to add the "Microsoft DAO v2.5 library".
Compile and run WSCVER16 (or WSCVER32) as the first example.
WSC32.DLL is written in standard ANSI C (WSC32.C), and has been compiled using Microsoft Visual C/C++ with the STDCALL and DECLSPEC compiler keywords. Source code (ANSI C) for the WSC library is provided in the registered version (if ordered) only.
For more information on the C/C++ version of WSC, download the latest version of WSC4C from our web site at http://www.marshallsoft.com/wsc4c.htm
The example programs are designed to demonstrate the various capabilities of WSC4VB. The best way to become familiar with WSC4VB is to study and run the example programs.
Most of the example programs can be compiled with any version of Microsoft Visual Basic. However, some require VB 4.0 or above (MESSAGE) while others require VB 5.0 or above (ATOK and THREAD). Before compiling with 16-bit Visual Basic (VB3 and 16-bit VB4), run READY16.BAT. All example programs are located in the APPS directory.
The WSCVER ("WSC Version") example program displays the WSC version number. This is the first program to compile and build since it verifies that WSC32.DLL (or WSC16.DLL) is installed properly. Use this with Visual Basic 3/4/5/6. The VB.NET version, WSCVER.VB is Section 5.1
EASY is a very simple communications program demonstrating basic serial communications functions. Everything that is typed on the keyboard is sent to the serial port, and everything incoming from the serial port is displayed on the screen.
The easiest way to test EASY is to connect to a modem. Typing 'AT' should result in an 'OK' being displayed.
A null-modem cable can also be used to connect two computers together with their serial ports. Run EASY on both machines. Whatever is typed on one machine will be displayed on the other.
Use this example with Visual Basic 3/4/5/6. The VB.NET version, EASY.VB is Section 5.2
SELFTEST performs a serial port I/O functionality test. Either a pair of ports on the same computer (using a null modem cable) or a single port (using a loopback adapter) can be tested.
Use this with Visual Basic 3/4/5/6. The VB.NET version, SELFTEST.VB is in Section 5.3
Refer to LOOPBACK.TXT in the DOCS directory for an explanation of how to make a loopback adapter (without tools!).
MODEM is similar to EASY, but with enhanced capability. It can set flow control (hardware, software, or none), DTR line (set or clear), RTS line (set or clear), display the transmit and receive queue sizes, detect a break signal, detect changes in DSR and CTS, as well as check for various line errors (parity error, framing error, data overrun, receive queue overflow, and transmit buffer full).
TERM is a simple terminal emulator suitable for calling up a BBS and downloading or uploading files using XMODEM or YMODEM. The TERM program uses MIO.DLL for modem control commands, ASD.DLL for the ASCII protocol, and the XYM.DLL for XMODEM & YMODEM protocol.
Selecting 'Dial' from the menu bar will result in a pop-up dialog requesting the phone number to dial. Once entered, the number is dialed, and the program will wait for up to 60 seconds for the 'CONNECT' string from the modem. This wait can be terminated at any time by choosing 'BREAK' on the menu bar.
Once logged on, files can be uploaded or downloaded by selecting 'Send' or 'Receive' from the menu bar. To abort a file transfer, choose 'BREAK' from the menu bar then type a series of Ctrl-X (^X) characters from the keyboard. Refer to TERM.TXT for more information.
4.6 FINDER
The FINDER program searches for a connected modem. Your modem must be connected to one of COM1, COM2, COM3, or COM4, and must be turned on.
The ATOK program demonstrates the use of the Visual Basic class "wscClass.cls". The program transmits an "AT" to the serial port, and receives the response. If the serial port is connected to a modem, sending an "AT" should result in "OK" being received and displayed.
The ATOK program uses classes, which were added to Visual Basic beginning with version 5.0
The DEVICE example program is designed to send a text string to a serial device. A carriage return is appended to the end of the string.
The DEVICE program can be used to send commands to serial devices which use ASCII commands, such as bar code readers, XY-plotters, etc.
The MESSAGE program is similar to EASY, except that rather than using a timer as in EASY, it uses the SioMessage function to request that WSC send a "Left Button Down" Windows message whenever any new serial data is available.
The MESSAGE example program requires Visual Basic 4.0 or above.
The XMS (XMODEM Send) and XMR (XMODEM Receive) programs are standalone programs which implement the XMODEM protocol. The YMS (YMODEM Send) and YMR (YMODEM Receive) programs are standalone programs that implement the YMODEM protocol.
The PUTTYPE example program demonstrates how to send user defined data across a serial port. Edit it as necessary before compiling. Use this with Visual Basic 3/4/5/6. The VB.NET version, XMS.VB & XMR.VB is in Section 5.4
Before building the Microsoft Visual Basic .NET (VB.NET) examples, be sure to read Section 2.9 "Using VB.Net" above.
This is the VB.Net equivalent of the VB 3/4/5/6 WSCVER example program in Section 4.1 above. The WSCVER example program displays the WSC version number.
Open the VB.Net project file wscver.vbproj
This is the VB.Net equivalent of the VB 3/4/5/6 EASY example program in Section 4.2 above. The EASY example program is a simple terminal program. Everything typed at the keyboard is sent out the serial port, and everything incoming from the serial port is displayed on the screen.
Open the VB.Net project file easy.vbproj
This is the VB.Net equivalent of the VB 3/4/5/6 SELFTEST example program in Section 4.3 above. The SELFTEST example program tests a serial port by connecting the serial port to be tested to a loopback adapter (easily made - see LOOPBACK.TXT) or to a modem.
Open the VB.Net project file selftest.vbproj
This is the VB.Net equivalent of the VB 3/4/5/6 XMS and XMR example programs in Section 4.11 above. XMS sends a file to the receiver such as XMR using the XMODEM protocol.
Open the VB.Net project file xms.vbproj for XMODEM/send. Open the VB.Net project file xmr.vbproj for XMODEM/receive.
NOTE: Version 2.0 was the first Visual Basic version.
Version 2.0: February 17, 1997.
Version 2.1: June 9, 1997.
Version 2.2: November 1, 1997.
Version 2.3: August 14, 1998
Version 2.4: June 1, 1999
Version 3.0: July 26, 2000
Version 3.1: May 1, 2001.
Version 3.2: July 30, 2002.
Version 4.0: November 21, 2003.
Version 4.1: August 12, 2004
Version 4.2: February 21, 2006.
Version 4.3: September 27, 2007.