should be simple: is computer on home network?

[bobD 6]

Basically, program needs to act differently if at home or away--so how do I know?

I've looked at using Winsock and

  HostEnt := gethostbyaddr(@SocketAddr.sin_addr.S_addr, 4, AF_INET);
and although that tells me if my home interbase server is available, in a dynamic DHCP environment that IP address isn't necessarily constant.

And a call to addr 192.168.1.1 (home router and default DNS gateway) returns nil: the peer computers respond, but the router doesn't.

Is there another way to get the name of the local network LAN that works both wired (desktop machines) and wifi?

 

I'd like to try using winsock's gethostbyname but I haven't found a good use example. Or is there a better way?

bobD

[aehimself 402]

When you are trying to detect your home network, don't rely on a successful (reverse) DNS lookup. I usually ping my home router (using fqdn) but even better, attempt a connection to a well-known service. However I only use this method to decide if VPN should be fired up or not; it's better to set up your DNS properly so tools will work from inside and outside.

 

If you are keen to go this way I found these two snipplets in my codebase:

Function LookupHostName(inIP: String): String;
Var
  host: PHostEnt;
  addr: Integer;
  dat: TWSAData;
Begin
  Result := '';
  
  WSAStartup($0101, dat);
  Try
    addr := inet_addr(PAnsiChar(AnsiString(inIP)));
    host := GetHostByAddr(@addr, 4, PF_INET);
    If host <> nil Then
      Result := String(host.h_name);
  Finally
    WSACleanup;
  End;
End;

This one was abandoned halfway as no variables seem to be declared:

  Write('Attempting to resolve ' + HostName + '...');

  If WSAStartup($0101, wsdata) = 0 Then
  Try
    tmp := GetHostByName(PAnsiChar(HostName));

    If tmp <> nil Then
    Begin
      tmpin.sin_addr.S_addr := LongInt(PLongInt(tmp^.h_addr_list^)^);
      IPAddress := inet_ntoa(tmpin.sin_addr);

      WriteLn(IPAddress);
    End;
  Finally
    WSACleanup;
  End;

May I ask why your program needs to behave different from a specific network? There might be a better way than relying on simple checks, which might trigger in places you don't want them to.

[Remy Lebeau 1572]

3 hours ago, bobD said:

Basically, program needs to act differently if at home or away--so how do I know?

Ask the user. The OS only knows whether there is a network connection or not. It doesn't care where the network is located or what it's connected to. That's up to the hardware to deal with.

Quote

Is there another way to get the name of the local network LAN that works both wired (desktop machines) and wifi?

No. And as far as sockets are concerned, there is no difference whatsoever whether you are connected to a wired LAN, or to a Wifi, or a cellular provider, etc.  The socket API works the same way. The difference is in how the hardware routes the traffic.

Quote

I'd like to try using winsock's gethostbyname but I haven't found a good use example.

Likely because this is not what that API is intended for.

Quote

Or is there a better way?

What EXACTLY are you trying to accomplish in the first place?

Edited 20 hours ago by Remy Lebeau

[Brian Evans 117]

There are network profiles in Windows which can be Private, Public or Domain. Normally your home network would be Private and anytime you go elsewhere it would be Public (discovery disabled) or Domain. You could check what the active connection is. Or just key off the active profile name for what network settings your application should use.

Snippet below for PowerShell.

 

Get-WmiObject MSFT_NetConnectionProfile -Namespace root/StandardCimv2 | 
       select Name,@{n='ActiveNetworkProfile';e={
         switch ($_.NetworkCategory){
             0 {'Public'}
             1 {'Private'}
             2 {'Domain'} 
             Default {$_.NetworkCategory}
            }
          }
        }

 

Edited 14 hours ago by Brian Evans

[aehimself 402]

5 hours ago, Brian Evans said:

There are network profiles in Windows which can be Private, Public or Domain. Normally your home network would be Private and anytime you go elsewhere it would be Public (discovery disabled) or Domain. You could check what the active connection is. Or just key off the active profile name for what network settings your application should use.

This check will trigger on all networks, which are set to private which is probably not a desired behavior. While these will work, OP's solution will be a different design pattern.

 

What if you put the code in a separate DLL, which you are not distributing; and lives only on your home dev PC?