1 Introduction

1.1 Features
1.2 Documentation Set
1.3 Example Program
1.4 Installation
1.5 Uninstalling
1.6 Pricing
1.7 Updates

2 CSC Library Overview

2.1 Dynamic Link Libraries
2.2 Keycode
2.3 INCLUDE Files
2.4 FoxPro Forms
2.5 Dynamic Strings
2.6 Null Terminated Strings
2.7 Win32 STDCALL and DECLSPEC
2.8 Adding CSC4FP to a VFP Program
2.9 Example Protocol
2.10 Error Display

3 Compiler Issues

3.1 Compiling Programs
3.2 Compiling to an Executable
3.3 Compiling CSC Source

4 Visual FoxPro Example Programs
5 Revision History

1 Introduction

The Client / Server Communications Library for Visual FoxPro (CSC4FP) is a toolkit that allows software developers to quickly develop server and client TCP/IP and UDP applications in Visual FoxPro.

The Client / Server Communications Library (CSC) is a component DLL library used to create server and client programs that can communicate with each other across any TCP/IP or UDP network such as the Internet or a private network (intranet or LAN [local area net]). The CSC component library uses the Windows API (Application Programmer's Interface) and Windows sockets API for all communication.

The CSC library can be used to communicate with other CSC programs, or they can be used to communicate with other TCP programs such as DNS, POP3, SMTP, FTP, HTTP, etc.

The Client / Server Communications Library for Visual FoxPro (CSC4FP) component library supports all 32-bit versions of Visual FoxPro. CSC4FP includes several Visual FoxPro example programs demonstrating client/server protocols, including examples that connect to HTTP (web) and POP3 servers as well as encrypt files.

A Win32 DLL is provided. CSC4FP runs under all versions of Windows (95/98/ME/2000/2003/NT/XP/Vista). The Client / Server Communications Library SDK DLL (CSC32.DLL) can also be used from any language (Visual C++, .NET, Visual Basic, VB.NET, ACCESS, EXCEL, VBA, Delphi, COBOL, Xbase++, Visual dBase, etc.) capable of calling the Windows API.

The Client/Server Communications Programmer's Manual provides information needed to compile programs using CSC in a Visual FoxPro programming environment.

When comparing the Client/Server Communications Library against our competition, note that:

• CSC is a standard Windows DLL (NOT an OCX or ActiveX control) and is much smaller than a comparable OCX or ActiveX control.
• Win32 DLL is included.
• CSC does NOT depend on ActiveX or Microsoft Foundation Class (MFC) or similar "support" libraries.
• CSC is fully thread-safe.
• CSC functions can be called from applications not capable of using controls.

MarshallSoft also has versions of the Client/Server Communications Library for C/C++ (CSC4C), Visual Basic (CSC4VB) and Delphi (CSC4D). Each version of CSC uses the same DLL (CSC32.DLL). However, the examples provided for each version are written for the specified programming language.

All versions of the Client/Server Communications Library (CSC) can be downloaded from our web site at

http://www.marshallsoft.com/client-server-communication.htm

Our goal is to provide a robust communication component library that you and your customers can depend upon. A fully functional evaluation version is available. Contact us if you have any questions.

1.1 Features

Some of the many features of the Client/Server Communications Library component are as follows:

• Supports both 32-bit and 64-bit Windows.
• Supports both UDP and TCP protocols.
• Can be used to create both client and server programs.
• Supports "one time" passwords for improved security.
• Can encrypt/decrypt data and files being transmitted.
• Supports challenge response authentication.
• Can send a Windows message when a connection is ready to accept.
• Can send a Windows message when incoming data is ready to be read.
• Can send and receive data buffers or entire files.
• Servers can handle multiple connections concurrently.
• Supports secure and private messaging.
• Create chat server and clients.
• Create client / server file transfer
• Create client programs to talk to TCP servers (POP3, IMAP, HTTP, SMTP, DNS)
• Create SMTP proxy programs extracting a copy of all recipient addresses
• Create POP3 proxy programs that filter incoming email for Spam
• Create HTTP proxy used to filter content
• Specify the maximum number of connections that the server will accept.
• Allows multiple servers and clients to run simultaneously.
  
  
• Royalty free distribution with your compiled application.
• Evaluation versions are fully functional. No unlock code is required.
• Is fully thread safe.
• Supports Windows 95/98/Me/NT/2000/2003/XP/Vista.
• Works with all versions of 32-bit Visual FoxPro
• Does not depend on support libraries. Makes calls to core Windows API functions only.
• Can be used with any program (in any language) capable of calling Windows API functions.
• Can be purchased with (or without) ANSI C source code.
• Updates are free for one year (Source code updates are separate).
• License covers all programming languages.
• Free unlimited one-year email and phone tech support for registered users.
• Documentation online as well as in printable format.

CSC can also be used to communicate with other CSC programs, or used to communicate with other TCP programs such as DNS, POP3, SMTP, FTP, HTTP, etc.

A good selection of Visual FoxPro example programs with full source code is included. Refer to Section 6 for more details on each of the example projects.

      cscver          Displays CSC version and build
      client          Simple client example program.
      server          Server example program.
      server2         Server example program (2 concurrent connections).
      download        Downloads text file from HTTP (web) server.
      FileGet         File server example that encrypts files.
      FilePut         File client example that decrypts files.
      pop3stat        Gets # emails waiting on POP3 server.
      hello           Form that displays CSC version and build.
      uNetTime        UDP client gets Network Time.

1.2 Documentation Set

The complete set of documentation consists of three manuals in two formats. This is the first manual (CSC_4FP) in the set.

• CSC4FP Programmer's Manual (CSC_4FP.PDF, CSC_4FP.HTM)
• CSC User's Manual (CSC_USR.PDF, CSC_USR.HTM)
• CSC Reference Manual (CSC_REF.PDF, CSC_REF.HTM)

Each manual comes in two formats:

• Adobe PDF (files ending in .PDF). The best format for printing manuals.
• Hyper Text (files ending in .HTM). Use any web browser to read.

The CSC_4FP Programmer's Manual is the language specific (Visual FoxPro) manual. All language dependent programming issues are discussed in this manual. Information needed to compile programs in a Visual FoxPro environment is provided in this manual.

The CSC User's Manual (CSC_USR) discusses language independent issues. Information on Client / Server protocols as well as purchasing and license information is provided in the manual.

The CSC Reference Manual (CSC_REF) contains details on each individual CSC function.

All manuals can be viewed online at

     http://www.marshallsoft.com/csc4fp.htm

1.3 Example Program

The following code segment attempts to connect to the server.

    DataSock = cscClient(@HostName, HostPort)
    if DataSock < 0
      ? "ERROR: " + Str(DataSock) + " cscClient fails"
      Buffer = Space(128)
      BufLen = cscErrorText(DataSock, @Buffer, 128)
      if BufLen > 0
        ? Left(Buffer, BufLen)
      endif
      Code = cscRelease()
      return
    endif
   ? "Connected to server"

Also see the example programs in the \CSC4FP\APPS sub-directory where CSC4FP was installed.

1.4 Installation

1. Before installation of CSC4FP, Visual FoxPro should already be installed.
   
   
2. Unzip CSC4FP60.ZIP(demo version) or CSCxxxxx.ZIP (registered version; xxxxx is the Customer ID) using any Windows unzip program.
   
   
3. Run the installation program SETUP.EXE which will install all CSC4FP files. SETUP will also copy CSC32.DLL to the Windows directory. No Windows system files are modified. Note that no DLL registration is required.

1.5 Uninstalling

Uninstalling CSC4FP is very easy. CSC does NOT modify the registry. First, delete the CSC4FP project directory created when installing CSC4FP. Second, delete CSC32.DLL from the Windows directory, typically C:\WINDOWS for Windows 95/98/Me/2003/XP/VISTA or C:\WINNT for Windows NT/2000.

1.6 Pricing

A developer license for the Client/Server Communications Library can be registered for $115 (or $195 with source code [ANSI C] to the library DLL). Purchasing details can be found in Section_1.4, "How to Purchase", of the CSC User's Manual (CSC_USR). See http://www.marshallsoft.com/csc_usr.htm#Section_1.4

Also see INVOICE.TXT or http://www.marshallsoft.com/order.htm

1.7 Updates

When a developer license is purchased for CSC, the developer will be sent a registered DLL plus a license file (CSCxxxxx.LIC). The license file can be used to update the registered DLL for a period of one year from purchase. Updates can be downloaded from

   
     http://www.marshallsoft.com/update.htm
   

After one year, the developer license must be updated to be able to download updates. The license can be updated for $30 if ordered within one year of the original purchase (or previous update). Between one year and three years, licenses can be updated for $55. After three years, updates are $75. Updates to the source code can be purchased for $40.

Note that the registered CSC DLL does not expire (only the ability to download updates expires).

2 CSC Library Overview

The Client/Server Communications Library (CSC) has been tested on multiple computers running Windows 95/98, Windows Me, Windows NT4, Windows 2000, Windows 2003, Windows XP and Windows Vista.

The CSC4FP library will work with all versions of 32-bit Visual FoxPro. The CSC32.DLL functions may be called by any Windows application program capable of calling the Windows API provided that the proper declaration file is used. CSC64.DLL is available to use with Win64 applications.

The SETUP installation program will copy the Lib's and DLL to the Windows directory. Refer to Section 1.4 "Installation". After SETUP is run, the CSC4FP files are copied to the directory specified (default \CSC4FP). Three sub-directories are created, as follows:

DOCS - All documentation files

APPS - All example code

DLLS - All DLL's

2.1 Dynamic Link Libraries

The Client/Server Communication Library component is a Win32 dynamic link library (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".

2.2 Keycode

CSC32.DLL has a keycode encoded within it. The keycode is a 9 or 10 digit decimal number (unless it is 0), and will be found in the file KEYCODE.FOX. The keycode for the evaluation version is 0. You will receive a new key code when registering. The KEYCODE is passed to cscAttach.

The keycode is not the customer ID (which is a 4 or 5 digit number).

If an error message (value -74) is returned when calling cscAttach , it means that the keycode in the CSC application does not match the keycode in the DLL. After registering, it is best to remove the evaluation version of the CSC32.DLL from the Windows search.

2.3 INCLUDE Files

All example programs include two files: KEYCODE.FOX and CSC32CON.FOX. The file CSC32CON.FOX contains all the necessary constants for CSC4FP, while the file KEYCODE.FOX contains the key code, as discussed in Section 2.2.

Since function declarations can not be in an INCLUDE file (at least through VFP version 9.0), they are listed in each program following the two INCLUDE files. The complete list of function declarations is also in the file CSC32FUN.FOX.

Due to the behavior of Visual FoxPro regarding INCLUDE files, it is strongly recommended that the INCLUDE files KEYCODE.FOX and CSC32CON.FOX be replaced with their contents in application programs (i.e., copy and paste contents) of the INCLUDE file.

2.4 FoxPro Forms

CSC functions can be called from any Visual FoxPro code module, such as programs, classes, and forms. See the HELLO.SCT example form.

2.5 Dynamic Strings

The Visual FoxPro language uses a technique known as "garbage collection" to manage string space at runtime, and may be called internally at any time by the FoxPro 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:

      BufLen = cscErrorText(ErrorCode, @Buffer, 128)
      if BufLen > 0
        ? Left(Buffer, BufLen)
      endif

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.

2.6 Null Terminated Strings

All strings returned from CSC functions are null terminated which means the end of the string is delimited by a Chr(0) character. These strings may be converted for FoxPro in one of two ways: (1) if the length of the string is known, use the FoxPro LEFT function: For example,

     * get server IP address
     TempBuffer = SPACE(TEMP_SIZE)
     Code = fceGetString(0, FCE_GET_SERVER_IP, @TempBuffer, TEMP_SIZE)
     if Code > 0
       ? "Server IP ", LEFT(TempBuffer, Code)
     endif

If the length of the null terminated string is not known, use the FoxPro AT function to find the position of Chr(0).

2.7 Win32 STDCALL and DECLSPEC

CSC32 is written in ANSI C and is compiled using the _stdcall and _declspec keywords. This means that CSC32 uses the same calling conventions and file naming conventions as the Win32 API. In particular, function names are NOT decorated. There are no leading underscores or trailing "@size" strings added to function names.

The CSC32.DLL functions may be called from any Windows application program capable of calling the Windows API provided that the proper declaration file is used.

2.8 Adding CSC to a VFP Program

1. Add the CSC constants (found in CSC32CON.FOX) that will be used in the developer's application.
2. Add the CSC function declarations (found in CSC32FUN.FOX) that will be called from the developer's application. Refer to the example programs.

2.9 Example Protocol

Several of the Client/Server Communications Library demonstration programs use the following example protocol:

1. The server must be running first at a specified IP address using a specified port number known to both client and server. A host name may be used instead of an IP address. The server waits for a connection attempt by a client.
2. The client attempts to connect to the server.
3. The server accepts the connection from the client, and then sends its greeting message, such as:

"CSC Example Server"

4. The client receives the server's greeting message.
5. The client sends a request (command) string to the server.
6. The server receives the client's request.
7. The server sends back its response string.
8. Repeat steps (5), (6), and (7) until done.
9. The client closes its connection to the server.

The server responds with the following response strings when presented with the corresponding requests (REQ) from the client:

     REQ   Response String               Request Example  Response Example
 
     WHO   Sends name of the server.     WHO              W_SERVER
     VER   Sends server version #.       VER              2.0
     BYE   OK (then disconnects)         BYE              OK
     ECHO  Sends string after "ECHO "    ECHO Hello       Hello

2.10 Error Display

3.1 Compiling Programs

3.2 Compiling to an Executable

     BUILD PROJECT C:\CSC4FP\APPS\CSCVER FROM C:\CSC4FP\APPS\CSCVER
     BUILD EXE C:\CSC4FP\APPS\CSCVER FROM C:\CSC4FP\APPS\CSCVER

FoxPro executables require VFP500.DLL and VFP5ENU.DLL (ENglish User), and may have to be copied from the VFP CDROM. If you are using an earlier or later version of FoxPro than version 5.0, substitute the appropriate DLL's for the above.

The FoxPro output display window will disappear as soon as your executable completes. In order to allow the user to control when the display window disappears, add the following code to your application, just before the final return.

     ?  " Type any key to exit..."
     X = InKey(0)

3.3 Compiling CSC Source

The source code for the CSC DLL's is written in standard ANSI C (CSC32.C), and has been compiled using Microsoft Visual C++. The Win32 version is compiled with the STDCALL and DECLSPEC compiler keywords. Source code for the CSC library can be purchased at the same time as a CSC developer license is purchased.

CSC may also be compiled using Borland C/C++ or Watcom C/C++ compilers. If you recompile CSC32.C is compiled using Borland or Watcom compilers, the resulting DLL can only be used by applications compiled with the same compiler, unless the STDCALL and DECLSPEC keywords are specified. For more information on the C/C++ version of CSC, download the latest version of CSC4C from our web site at http://www.marshallsoft.com/client-server-communication.htm

4 Visual FoxPro Example Programs

All example programs are written for 32-bit FoxPro. Each has been tested and shows how to correctly use CSC functions. It suggested that the developer compile and run the example programs before developing an application using CSC4FP.

Because of the peculiarity of Visual FoxPro regarding INCLUDE files, it is highly recommended that the INCLUDE files KEYCODE.FOX and CSC32CON.FOX be replaced with their contents.

Refer to Section 3.1 above for information on compiling and linking the example programs. CSC functions may also be called from Visual FoxPro projects.

4.1 CSCVER

The CSCVER ("CSC Version") example program (CSCVER.PRG) displays the CSC version number. This is the first program to compile and build since it verifies that CSC32.DLL is installed properly.

4.2 CLIENT

The CLIENT example program (CLIENT.PRG) operates as a client that connects to the example server program (SERVER). Edit CLIENT.PRG with your host name or server's IP address before compiling. Start the CLIENT program after the SERVER program.

4.3 SERVER

The SERVER example program (SERVER.PRG) operates as a server that accepts connections from the example client program (CLIENT). Edit SERVER.PRG with your host name or IP address before compiling.

4.4 SERVER2

The SERVER2 example program (SERVER2.PRG) operates as a server that accepts multiple connections from the example client program (CLIENT). Edit SERVER2.PRG with your host name or IP address before compiling.

SERVER2 accepts a maximum of two connections (clients) at any one time.

4.5 FileGet

The FileGet example program (FileGet.PRG) operates as a SERVER, and receives files from the FilePut client. Files are decrypted when received. Edit FileGet.PRG with the host name or server IP address before compiling. Start FileGet before FilePut.

4.6 FilePut

The FilePut example program (FilePut.PRG) operates as a CLIENT, and sends files to the FileGet server. Files are encrypted when sent. Edit FilePut.PRG with the host name or server IP address before compiling.

4.7 FileGet2

The FileGet2 example program (FileGet2.PRG) operates as a CLIENT, and receives files from the FilePut2 server. Files are decrypted when received. Edit FileGet2.PRG with the host name or server IP address before compiling. Start FileGet2 before FilePut2.

4.8 FilePut2

The FilePut2 example program (FilePut2.PRG) operates as a SERVER, and sends files to the FileGet2 client. Files are encrypted when sent. Edit FilePut2.PRG with the host name or server IP address before compiling.

4.9 Download

The Download example client program (Download.PRG) connects to the MarshallSoft web site (HTTP server) and downloads a file from the ./files directory.

4.10 POP3Stat

The POP3Stat example client program (POP3Stat.PRG) logs onto a POP3 account and returns the number of emails waiting. Edit POP3Stat.PRG with the POP3 Server name, user name and password before compiling.

4.11 HELLO

The Hello example form displays the CSC version and build number when the command button is pressed.

From the VFP menu (File/Open), open the form HELLO.SCX (with "File of Type: Form"). When the "Form" menu tab appears on the VFP menu bar, choose "Run Form". This form can also be opened from the VFP command window by typing "modify form \csc4fp\apps\hello.scx".

4.12 uNetTime

uNetTime is an example UDP client that connects to a Network Time Server (on well known port 37) and gets the network time (seconds since 1 January 1900 GMT) from the server. The default server is

time-A.timefreq.bldrdoc.gov

5 Revision History

CSC32.DLL is written in ANSI C. All language versions of CSC (C/C++, Visual Basic, Delphi, and FoxPro) use the same identical DLL.

Version 5.0: October 15, 2008

Initial Visual FoxPro release of CSC.

Version 6.0: August 17, 2009

• Supports 64-bits (CSC64.DLL), although FoxPro through 2009 does not.
• Added cscPutPacket and cscGetPacket.
• Added cscCryptoPutPacket and cscCryptoGetPacket.
• Added CSC_SET_MAX_PACKET_SIZE and CSC_GET_MAX_PACKET_SIZE.
• Changed: NBR_DATA_SOCKS to 1000, NBR_LISTEN_SOCKS to 50.
• Changed: MAX_FILE_BUFFER_SIZE to 30000.
• Changed: DEFAULT_FILE_BUFFER_SIZE to 10000.
• Added CSC_SET_PAD_TX_INDEX and CSC_SET_PAD_RX_INDEX.
• Added cscDataCRC and cscFileCRC.
• cscGetInteger(Chan, CSC_GET_SOCKET) returns actual socket.
• Added cscCreateUDP, cscGetUDP, cscCreateUDP.
• Added cscNetToHost32.