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   <TITLE>Section - Parse IP addresses</TITLE>
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Parse IP addresses
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This article was contributed by <A HREF="mailto:nikolay@jriver.com">Nikolay Sokratov</A>.

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<A HREF="ddx_ipaddress.zip">Download Source Code and Example</A>
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<p>Very often, if you write Internet applications, you need to verify IP address
user entered and make sure that it's correct. So lets see how we can do that without
a lot of troubles.<br>
First of all we need to add declarations of the following function to header file of the
dialog.

<FONT COLOR="#990000"><TT><PRE>
#include &lt;winsock.h&gt;

void WINAPI DDX_IPAddress(CDataExchange* pDX, int nIDC, UINT & value);
</tt></PRE></FONT>

To implement data exchange you need to call DDX_IPAddress function from
within your dialog DoDataExchange function<BR>
Now add following code to the implementation file of the dialog, and do not forget
to include <b>ws2_32.lib</b> into the project or you'll get a lot of linking errors.
<FONT COLOR="#990000"><TT><PRE>
// DDX routine fo IP address translation
void WINAPI DDX_IPAddress(CDataExchange* pDX, int nIDC, UINT & value)
{
	// from dialog to class ?
	if( pDX->m_bSaveAndValidate)
	{
		CString Val;
		BOOL bValid = true;

		pDX->m_pDlgWnd->GetDlgItem(nIDC)->GetWindowText(Val);

		for( int i = 0; i < Val.GetLength(); i++)
		{
			// let's check if all entered char in entered
			// IP address are digits
			if(Val[i] == '.')
				continue;

			if(isdigit(Val[i]) == 0)
			{
				bValid = false;
				break;			
			}
		}

		if(bValid)
		{
			value = inet_addr(Val);
			if(value == INADDR_NONE)
			{
				pDX->m_pDlgWnd->MessageBox("The entered IP address is invalid.");
				pDX->PrepareEditCtrl(nIDC);
				pDX->Fail();
			}
		}
		else
		{
			pDX->m_pDlgWnd->MessageBox("IP address can only have digits and dots.");
			pDX->PrepareEditCtrl(nIDC);
			pDX->Fail();
		}
	}
	else
	{
		// if the value is a valid IP address store it in the child control
		in_addr IPaddress;
		memcpy(&IPaddress, &value, 4);
		CString Address = inet_ntoa(IPaddress);
		if(!Address.IsEmpty())
		{
			pDX->m_pDlgWnd->GetDlgItem(nIDC)->SetWindowText(Address);
		}
	}	
}
</tt></PRE></FONT>

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<p>Last updated: 14 May 1998

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