This chapter covers most used WinInet APIs with sample code. I don't see any use of Gopher protocol these days, so I will skip that part for now.

WinInet HTTP APIs

Here is WinInet HTTP APIs hierarchy. To use an Http API, you have to go through the heirarchy. 



Before using any HTTP functions, you must be aware of InternetConnect funtion. Here is syntax for InternetConnect.

HINTERNET InternetConnect(IN HINTERNET hInternetSession, IN LPCSTR lpszServerName, IN INTERNET_PORT nServerPort, IN LPCSTR lpszUsername, IN LPCSTR lpszPassword, IN DWORD dwService, IN DWORD dwFlags, IN DWORD dwContext );

Where hInternetSession is handle retured by InternetOpen. Parameter lpszServerName is name of the server (a host name or host IP). The next parameter, nServerPort allows you to specify a port number. Here are default values for this parameter:

Here is an example:

HINTERNET hConnection = InternetConnect( hSession, "www.dotnetheaven.com", INTERNET_DEFAULT_HTTP_POST, NULL, NULL, INTERNET_SERVICE_HTTP, 0, 0 );

Here is a list of HTTP APIs:

Here is how to use this function:

HttpSendRequest( hData, NULL, 0, NULL, 0);

Example: Now let's see how to use all these functions in our example. This example shows how to download contents of a page using HTTP API functions.

HINTERNET hINet, hConnection, hData;
CHAR buffer[2048] ;
CString m_strContents ;
DWORD dwRead, dwFlags, dwStatus ;
hINet = InternetOpen("InetURL/1.0", INTERNET_OPEN_TYPE_PRECONFIG, NULL, NULL, 0 );
if ( !hINet )
{
AfxMessageBox("InternetOpen Failed");
return;
}
try
{
hConnection = InternetConnect( hINet, "www.dotnetheaven.com", 80, " "," ", INTERNET_SERVICE_HTTP, 0, 0 );
if ( !hConnection )
{
InternetCloseHandle(hINet);
return;
}
// Get datahData = HttpOpenRequest( hConnection, "GET", "/uicsa/index.htm", NULL, NULL, NULL, INTERNET_FLAG_KEEP_CONNECTION, 0 );
if ( !hData )
{
InternetCloseHandle(hConnection);
InternetCloseHandle(hINet);
return;
}
HttpSendRequest( hData, NULL, 0, NULL, 0);
while( InternetReadFile( hData, buffer, 255, &dwRead ) )
{
if ( dwRead == 0 )
return;
buffer[dwRead] = 0;
m_strContents += buffer;
}
}
catch( CInternetException* e)
{
e->ReportError();
e->Delete();
}
InternetCloseHandle(hConnection);InternetCloseHandle(hINet);
InternetCloseHandle(hData);

HttpAddRequestHeaders

You can add, replace or remove headers to your HTTP request by using this function. Add, replace, or remove depends on dwModifiers parameter. Ok, here is the syntax:

BOOL HttpAddRequestHeaders( IN HINTERNET hHttpRequest, IN LPCSTR lpszHeaders,    IN DWORD dwHeadersLength,  IN DWORD dwModifiers);

FtpCreateDirectory

This function creates a directory on the FTP server.

Syntax:

BOOL FtpCreateDirectory(IN HINTERNET hConnect, IN LPCTSTR lpszDirectory );

Sample:

if (!FtpCreateDirectory(g_hConnection, "NewDir"))
DoSomething();

FtpDeleteFile

This function deletes a file from the FTP server. Nothing to explain here :). Here is the syntax:

BOOL FtpDeleteFile( IN HINTERNET hConnect, IN LPCTSTR lpszFileName);

Sample:

if (!FtpDeleteFile(g_hConnection, strFileName))
DoSomething();

FtpFindFirstFile

This function finds a file on the FTP server and help InternetFindNextFile to find files on the server.

Syntax:

HINTERNET FtpFindFirstFile(IN HINTERNET hConnect,IN LPCTSTR lpszSearchFile,    OUT LPWIN32_FIND_DATA lpFindFileData, IN DWORD dwFlags, IN DWORD_PTR dwContext );

Sample:

CString strFileName = "mcb.asp";
WIN32_FIND_DATA FindFileData;
HINTERNET hFindFile=NULL;
m_RemoteList.ResetContent();
if (hFindFile)
InternetCloseHandle(hFindFile);
hFindFile = FtpFindFirstFile(g_hConnection, szFileName, &FindFileData, INTERNET_FLAG_RELOAD, 0);
if (hFindFile)
{
if ( (FindFileData.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) == FILE_ATTRIBUTE_DIRECTORY )
strFileName.Format("%s <DIR>", FindFileData.cFileName);
else
strFileName = FindFileData.cFileName;
m_RemoteList.AddString(strFileName);
while(InternetFindNextFile(hFindFile, &FindFileData))
{
if ( (FindFileData.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) == FILE_ATTRIBUTE_DIRECTORY )
strFileName.Format("%s <DIR>", FindFileData.cFileName);
else
strFileName = FindFileData.cFileName;
m_RemoteList.AddString(strFileName);
}
InternetCloseHandle(hFindFile);
}

FtpGetCurrentDirectory

This function returns the current active directory of the FTP server. All FTP function applies to current active directory. So this function is plays an important role.

Syntax:

BOOL FtpGetCurrentDirectory(IN HINTERNET hConnect,OUT LPTSTR lpszCurrentDirectory,    IN OUT LPDWORD lpdwCurrentDirectory);

Sample:

char szDir[255];
DWORD dwLen = 255;
//get the current remote directory
if (!FtpGetCurrentDirectory(g_hConnection, szDir, &dwLen))
DoSomething();

FtpGetFile

This function retrieves a file from the FTP server and stores on the local system. Here is the syntax:

BOOL FtpGetFile(IN HINTERNET hConnect, IN LPCTSTR lpszRemoteFile, IN LPCTSTR                lpszNewFile, IN BOOL fFailIfExists,IN DWORD dwFlagsAndAttributes,IN DWORD dwFlags,IN DWORD_PTR dwContext);
 
FtpGetFileSize

Retrieves the file size of the requested FTP resource.

Syntax:

DWORD FtpGetFileSize(IN HINTERNET hFile, OUT LPDWORD lpdwFileSizeHigh);
 
FtpOpenFile

Initiates access to a remote file on an FTP server for reading or writing.

Syntax:

HINTERNET FtpOpenFile (IN HINTERNET hConnect,IN LPCTSTR lpszFileName,IN DWORD dwAccess, IN DWORD dwFlags,IN DWORD_PTR dwContext);

FtpPutFile

Send a local file on the FTP server.

Syntax:

BOOL FtpPutFile(IN HINTERNET hConnect,IN LPCTSTR lpszLocalFile,IN LPCTSTR lpszNewRemoteFile, IN DWORD dwFlags,IN DWORD_PTR dwContext);
DWORD dwFlags;
if (m_lMode == MODE_ASCII) 
dwFlags = FTP_TRANSFER_TYPE_ASCII;
else  
dwFlags = FTP_TRANSFER_TYPE_BINARY;
BOOL bRet = FtpPutFile(g_hConnection, szLocalFile, szRemoteFile, dwFlags, 0);

FtpRemoveDirectory

Removes the specified directory on the FTP server.

Syntax:

BOOL FtpRemoveDirectory(IN HINTERNET hConnect,IN LPCTSTR lpszDirectory)
 
FtpRenameFile

Renames a file stored on the FTP server.

Syntax:

BOOL FtpRenameFile(IN HINTERNET hConnect,IN LPCTSTR lpszExisting,IN LPCTSTR lpszNew);

FtpSetCurrentDirectory Function

Change to a different working directory on the FTP server.

Syntax:

BOOL FtpSetCurrentDirectory(IN HINTERNET hConnect,IN LPCTSTR lpszDirectory);

Other chapters of this tutorial

• Introduction to WinInet.
• Working with Common WinInet APIs. 
• WinInet MFC classes with sample examples. 
• Advanced WinInet and Security Issues.