[fpc-pascal] lNet getting the local IP

[silvioprog]

Hi Brian,

I tested again, and discovered that's not is necessary a connection to a
web.
I changed to 0.0.0.0 and returned 127.0.0.1, perfect! :)

I will use this function. Thanks very much again. :)

2010/10/7 Brian Winfrey <bwcode4u at gmail.com>

> >> On 06/10/10 14:27, Felipe Monteiro de Carvalho wrote:
> >>> Ok, thanks everyone, it seams that I managed to extract a function
> >>> from Silvio's code which doesn't use Synapse. I only tested in Windows
> >>> so far:
> >>>
> >>> unit chesstcputils;
> >>>
> >>> {$mode objfpc}{$H+}
> >>>
> >>> interface
> >>>
> >>> uses
> >>>    {$IFDEF MSWINDOWS}
> >>>    Winsock,
> >>>    {$ENDIF}
> >>>    Classes, SysUtils;
> >>>
> >>> function ChessGetLocalIP(): string;
> >>>
> >>> implementation
> >>>
> >>> const
> >>>    CFormatIPMask = '%d.%d.%d.%d';
> >>>
> >>> function ChessGetLocalIP(): string;
> >>> var
> >>>    I, VAttempt: Integer;
> >>>    VStrTemp, VSitesToTry: TStringList;
> >>> {$IFDEF UNIX}
> >>>    VProcess: TProcess;
> >>> {$ENDIF}
> >>> {$IFDEF MSWINDOWS}
> >>> var
> >>>    VWSAData: TWSAData;
> >>>    VHostEnt: PHostEnt;
> >>>    VName: string;
> >>> {$ENDIF}
> >>> begin
> >>>    Result := '';
> >>> {$IFDEF UNIX}
> >>>        VStrTemp := TStringList.Create;
> >>>        VProcess := TProcess.Create(nil);
> >>>        try
> >>>          VProcess.CommandLine :=
> >>>            'sh -c "ifconfig eth0 | awk ''/inet end/ {print $3}''"';
> >>
> >> Yuck.  This doesn't work on my system (debian).  If you really want the
> >> least effort, you may have more luck with simply parsing `hostname -I`
> >> somehow.  The right way to do this is with an ioctl, I believe
> >> (SIOCGIFCONF).  Look here:
> >>
> >> http://www.kernel.org/doc/man-pages/online/pages/man7/netdevice.7.html
> >>
> >> I'm sure there's some code floating around, but it probably means that
> >> you have to translate some headers :(.
> >>
> >> Henry
> >>
> > Re: [fpc-pascal] lNet getting the local IP
> >>
> >
> > I found an example for linux on stack overflow that was in c
> >
> http://stackoverflow.com/questions/212528/linux-c-get-the-ip-address-of-local-computer
> >
> > - here is a rough translation:
> >
> > program GetPrimaryIpAddress;
> > {$mode objfpc}
> >
> > uses
> >  baseunix,
> >  unixtype,
> >  sockets,
> >  SysUtils;
> >
> > procedure Get(var buf: array of char; const len: longint);
> > const
> >  CN_GDNS_ADDR = '8.8.8.8';
> >  CN_GDNS_PORT = 53;
> > var
> >  s: string;
> >  sock: longint;
> >  err: longint;
> >  HostAddr: TSockAddr;
> >  l: Integer;
> >  UnixAddr: TInetSockAddr;
> >
> > begin
> >  err := 0;
> >  Assert(len >= 16);
> >
> >  sock := fpsocket(AF_INET, SOCK_DGRAM, 0);
> >  assert(sock <> -1);
> >
> >  UnixAddr.family := AF_INET;
> >  UnixAddr.port := htons(CN_GDNS_PORT);
> >  UnixAddr.addr := StrToHostAddr(CN_GDNS_ADDR).s_addr;
> >
> >  if (fpConnect(sock, at UnixAddr,SizeOf(UnixAddr)) = 0) then
> >  begin
> >    try
> >      l := SizeOf(HostAddr);
> >      if (fpgetsockname(sock, @HostAddr, @l) = 0) then
> >      begin
> >        s := NetAddrToStr(HostAddr.sin_addr);
> >        StrPCopy(PChar(Buf), s);
> >      end
> >      else
> >      begin
> >        err:=socketError;
> >      end;
> >    finally
> >      if (fpclose(sock) <> 0) then
> >      begin
> >        err := socketError;
> >      end;
> >    end;
> >  end
> >  else
> >  begin
> >    err:=socketError;
> >  end;
> >
> >  if (err <> 0) then
> >  begin
> >    // report error
> >  end;
> > end;
> >
> > var
> >  ipbuf: array[0..255] of char;
> >
> > begin
> >  system.FillChar(ipbuf, sizeOf(ipBuf), #0);
> >  Get(ipbuf, system.SizeOf(ipbuf));
> >  WriteLn(StrPas(ipbuf));
> > end.
> >
> > BrianW
> >
> I have tried this code with multiple scenarios.
>
> if interfaces are down, no ip address is returned. I would say that is
> expected as there is no network.
> ifconfig will return same. only lo has an address 127.0.0.1.
>
> Otherwise I get the primary ip address as long as routing is used.
>
> if connecting to 0.0.0.0, 127.0.0.1 is returned
>
> Use 127.0.0.1 and the primary is returned.
>
> Run some tests and let me know what you find.

-- 
Silvio Clécio,
*programmer* *ObjectPascal*
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