Detect an internet connection activation with Delphi
I worked on a project to run a user's logon script whenever they connected our network over VPN. To do this, I wrote a helper unit that retrieves adapter info and stores it into a simple record.
I then setup up a registry notification, see here for how to do that in Delphi
The registry notification was on HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces. This notification event fires every time Windows obtains a new IP address, or makes any type of change to an adapters connection information. When this event fired, I called the function (in the code below) to retrieve updated information about the adapter. I compared this new information to my previously recorded information...meaning I had to save the previous adapter info query in order to know if something had changed.
Anyhow, here is my helper unit:
unit uAdapterInfo;
interface
uses
Classes,
SysUtils;
const
MAX_INTERFACE_NAME_LEN = $100;
ERROR_SUCCESS = 0;
MAXLEN_IFDESCR = $100;
MAXLEN_PHYSADDR = 8;
MIB_IF_OPER_STATUS_NON_OPERATIONAL = 0;
MIB_IF_OPER_STATUS_UNREACHABLE = 1;
MIB_IF_OPER_STATUS_DISCONNECTED = 2;
MIB_IF_OPER_STATUS_CONNECTING = 3;
MIB_IF_OPER_STATUS_CONNECTED = 4;
MIB_IF_OPER_STATUS_OPERATIONAL = 5;
MIB_IF_TYPE_OTHER = 1;
MIB_IF_TYPE_ETHERNET = 6;
MIB_IF_TYPE_TOKENRING = 9;
MIB_IF_TYPE_FDDI = 15;
MIB_IF_TYPE_PPP = 23;
MIB_IF_TYPE_LOOPBACK = 24;
MIB_IF_TYPE_SLIP = 28;
MIB_IF_ADMIN_STATUS_UP = 1;
MIB_IF_ADMIN_STATUS_DOWN = 2;
MIB_IF_ADMIN_STATUS_TESTING = 3;
_MAX_ROWS_ = 20;
ANY_SIZE = 1;
type
MIB_IFROW = record
wszName: array[0 .. (MAX_INTERFACE_NAME_LEN * 2 - 1)] of ansichar;
dwIndex: longint;
dwType: longint;
dwMtu: longint;
dwSpeed: longint;
dwPhysAddrLen: longint;
bPhysAddr: array[0 .. (MAXLEN_PHYSADDR - 1)] of byte;
dwAdminStatus: longint;
dwOperStatus: longint;
dwLastChange: longint;
dwInOctets: longint;
dwInUcastPkts: longint;
dwInNUcastPkts: longint;
dwInDiscards: longint;
dwInErrors: longint;
dwInUnknownProtos: longint;
dwOutOctets: longint;
dwOutUcastPkts: longint;
dwOutNUcastPkts: longint;
dwOutDiscards: longint;
dwOutErrors: longint;
dwOutQLen: longint;
dwDescrLen: longint;
bDescr: array[0 .. (MAXLEN_IFDESCR - 1)] of ansichar;
end;
type
MIB_IPADDRROW = record
dwAddr: longint;
dwIndex: longint;
dwMask: longint;
dwBCastAddr: longint;
dwReasmSize: longint;
unused1: word;
unused2: word;
end;
type
_IfTable = record
nRows: longint;
ifRow: array[1.._MAX_ROWS_] of MIB_IFROW;
end;
type
_IpAddrTable = record
dwNumEntries: longint;
table: array[1..ANY_SIZE] of MIB_IPADDRROW;
end;
function GetIfTable(pIfTable: Pointer; var pdwSize: longint; bOrder: longint): longint;
stdcall;
function GetIpAddrTable(pIpAddrTable: Pointer; var pdwSize: longint;
bOrder: longint): longint; stdcall;
function Get_if_type(iType: integer): string;
function Get_if_admin_status(iStatus: integer): string;
function Get_if_oper_status(iStatus: integer): string;
implementation
function GetIfTable; stdcall; external 'IPHLPAPI.DLL';
function GetIpAddrTable; stdcall; external 'IPHLPAPI.DLL';
function Get_if_type(iType: integer): string;
var
sResult: string;
begin
sResult := 'UNKNOWN';
case iType of
1: sResult := 'Other';
6: sResult := 'Ethernet';
9: sResult := 'Tokenring';
15: sResult := 'FDDI';
23: sResult := 'PPP';
24: sResult := 'Local loopback';
28: sResult := 'SLIP';
37: sResult := 'ATM';
71: sResult := 'IEEE 802.11';
131: sResult := 'Tunnel';
144: sResult := 'IEEE 1394 (Firewire)';
end;
Result := sResult;
end;
function Get_if_admin_status(iStatus: integer): string;
var
sResult: string;
begin
sResult := 'UNKNOWN';
case iStatus of
1: sResult := 'UP';
2: sResult := 'DOWN';
3: sResult := 'TESTING';
end;
Result := sResult;
end;
function Get_if_oper_status(iStatus: integer): string;
var
sResult: string;
begin
sResult := 'UNKNOWN';
case iStatus of
0: sResult := 'NON_OPERATIONAL';
1: sResult := 'UNREACHABLE';
2: sResult := 'DISCONNECTED';
3: sResult := 'CONNECTING';
4: sResult := 'CONNECTED';
5: sResult := 'OPERATIONAL';
end;
Result := sResult;
end;
end.
To use this unit from another unit, I created the following function, which populated a custom type called TAdapterInfo (declared in my main unit):
type
TAdapterInfo = array of record
dwIndex: longint;
dwType: longint;
dwMtu: longint;
dwSpeed: extended;
dwPhysAddrLen: longint;
bPhysAddr: string;
dwAdminStatus: longint;
dwOperStatus: longint;
dwLastChange: longint;
dwInOctets: longint;
dwInUcastPkts: longint;
dwInNUcastPkts: longint;
dwInDiscards: longint;
dwInErrors: longint;
dwInUnknownProtos: longint;
dwOutOctets: longint;
dwOutUcastPkts: longint;
dwOutNUcastPkts: longint;
dwOutDiscards: longint;
dwOutErrors: longint;
dwOutQLen: longint;
dwDescrLen: longint;
bDescr: string;
sIpAddress: string;
sIpMask: string;
end;
//////////
function Get_EthernetAdapterDetail(var AdapterDataFound: TAdapterInfo): boolean;
var
pIfTable: ^_IfTable;
pIpTable: ^_IpAddrTable;
ifTableSize, ipTableSize: longint;
tmp: string;
i, j, k, m: integer;
ErrCode: longint;
sAddr, sMask: in_addr;
IPAddresses, IPMasks: TStringList;
sIPAddressLine, sIPMaskLine: string;
bResult: boolean;
begin
bResult := True; //default return value
pIfTable := nil;
pIpTable := nil;
IPAddresses := TStringList.Create;
IPMasks := TStringList.Create;
try
// First: just get the buffer size.
// TableSize returns the size needed.
ifTableSize := 0; // Set to zero so the GetIfTabel function
// won't try to fill the buffer yet,
// but only return the actual size it needs.
GetIfTable(pIfTable, ifTableSize, 1);
if (ifTableSize < SizeOf(MIB_IFROW) + Sizeof(longint)) then
begin
bResult := False;
Result := bResult;
Exit; // less than 1 table entry?!
end;
ipTableSize := 0;
GetIpAddrTable(pIpTable, ipTableSize, 1);
if (ipTableSize < SizeOf(MIB_IPADDRROW) + Sizeof(longint)) then
begin
bResult := False;
Result := bResult;
Exit; // less than 1 table entry?!
end;
// Second:
// allocate memory for the buffer and retrieve the
// entire table.
GetMem(pIfTable, ifTableSize);
ErrCode := GetIfTable(pIfTable, ifTableSize, 1);
if ErrCode <> ERROR_SUCCESS then
begin
bResult := False;
Result := bResult;
Exit; // OK, that did not work.
// Not enough memory i guess.
end;
GetMem(pIpTable, ipTableSize);
ErrCode := GetIpAddrTable(pIpTable, ipTableSize, 1);
if ErrCode <> ERROR_SUCCESS then
begin
bResult := False;
Result := bResult;
Exit;
end;
for k := 1 to pIpTable^.dwNumEntries do
begin
sAddr.S_addr := pIpTable^.table[k].dwAddr;
sMask.S_addr := pIpTable^.table[k].dwMask;
sIPAddressLine := Format('0x%8.8x', [(pIpTable^.table[k].dwIndex)]) +
'=' + Format('%s', [inet_ntoa(sAddr)]);
sIPMaskLine := Format('0x%8.8x', [(pIpTable^.table[k].dwIndex)]) +
'=' + Format('%s', [inet_ntoa(sMask)]);
IPAddresses.Add(sIPAddressLine);
IPMasks.Add(sIPMaskLine);
end;
SetLength(AdapterDataFound, pIfTable^.nRows); //initialize the array or records
for i := 1 to pIfTable^.nRows do
try
//if pIfTable^.ifRow[i].dwType=MIB_IF_TYPE_ETHERNET then
//begin
m := i - 1;
AdapterDataFound[m].dwIndex := 4;//(pIfTable^.ifRow[i].dwIndex);
AdapterDataFound[m].dwType := (pIfTable^.ifRow[i].dwType);
AdapterDataFound[m].dwIndex := (pIfTable^.ifRow[i].dwIndex);
AdapterDataFound[m].sIpAddress :=
IPAddresses.Values[Format('0x%8.8x', [(pIfTable^.ifRow[i].dwIndex)])];
AdapterDataFound[m].sIpMask :=
IPMasks.Values[Format('0x%8.8x', [(pIfTable^.ifRow[i].dwIndex)])];
AdapterDataFound[m].dwMtu := (pIfTable^.ifRow[i].dwMtu);
AdapterDataFound[m].dwSpeed := (pIfTable^.ifRow[i].dwSpeed);
AdapterDataFound[m].dwAdminStatus := (pIfTable^.ifRow[i].dwAdminStatus);
AdapterDataFound[m].dwOperStatus := (pIfTable^.ifRow[i].dwOperStatus);
AdapterDataFound[m].dwInUcastPkts := (pIfTable^.ifRow[i].dwInUcastPkts);
AdapterDataFound[m].dwInNUcastPkts := (pIfTable^.ifRow[i].dwInNUcastPkts);
AdapterDataFound[m].dwInDiscards := (pIfTable^.ifRow[i].dwInDiscards);
AdapterDataFound[m].dwInErrors := (pIfTable^.ifRow[i].dwInErrors);
AdapterDataFound[m].dwInUnknownProtos := (pIfTable^.ifRow[i].dwInUnknownProtos);
AdapterDataFound[m].dwOutNUcastPkts := (pIfTable^.ifRow[i].dwOutNUcastPkts);
AdapterDataFound[m].dwOutUcastPkts := (pIfTable^.ifRow[i].dwOutUcastPkts);
AdapterDataFound[m].dwOutDiscards := (pIfTable^.ifRow[i].dwOutDiscards);
AdapterDataFound[m].dwOutErrors := (pIfTable^.ifRow[i].dwOutErrors);
AdapterDataFound[m].dwOutQLen := (pIfTable^.ifRow[i].dwOutQLen);
AdapterDataFound[m].bDescr := (pIfTable^.ifRow[i].bDescr);
tmp := '';
for j := 0 to pIfTable^.ifRow[i].dwPhysAddrLen - 1 do
begin
if Length(tmp) > 0 then
tmp := tmp + '-' + format('%.2x', [pIfTable^.ifRow[i].bPhysAddr[j]])
else
tmp := tmp + format('%.2x', [pIfTable^.ifRow[i].bPhysAddr[j]]);
end;
if Length(tmp) > 0 then
begin
AdapterDataFound[m].bPhysAddr := tmp;
end;
except
bResult := False;
Result := bResult;
Exit;
end;
finally
if Assigned(pIfTable) then
begin
FreeMem(pIfTable, ifTableSize);
end;
FreeAndNil(IPMasks);
FreeAndNil(IPAddresses);
end;
Result := bResult;
end;
On a completely side note, I also used this unit and almost exact same code to create a duplicate of ifconfig -a, which can be found on github. I mainly did it as an exercise in teaching myself how to accomplish this task.
uses WinInet;
function IsConnected: boolean;
const
// local system uses a modem to connect to the Internet.
INTERNET_CONNECTION_MODEM = 1;
// local system uses a local area network to connect to the Internet.
INTERNET_CONNECTION_LAN = 2;
// local system uses a proxy server to connect to the Internet.
INTERNET_CONNECTION_PROXY = 4;
// local system's modem is busy with a non-Internet connection.
INTERNET_CONNECTION_MODEM_BUSY = 8;
var
dwConnectionTypes : DWORD;
begin
dwConnectionTypes := INTERNET_CONNECTION_MODEM +
INTERNET_CONNECTION_LAN +
INTERNET_CONNECTION_PROXY;
Result := InternetGetConnectedState(@dwConnectionTypes,0);
end;
Look at InternetGetConnectedState in WinINet.
Some applications might also poll for a known server and not do anything until they get a valid connection.
Here's a working example of how to use the helper unit. It is from a small project I wrote to emulate "ifconfig -a". This is a console application project.
program ifconfig;
{$APPTYPE CONSOLE}
uses
SysUtils,
Classes,
Winsock,
uAdapterInfo in 'uAdapterInfo.pas';
type
TAdapterInfo = array of record
dwIndex: longint;
dwType: longint;
dwMtu: longint;
dwSpeed: extended;
dwPhysAddrLen: longint;
bPhysAddr: string;
dwAdminStatus: longint;
dwOperStatus: longint;
dwLastChange: longint;
dwInOctets: longint;
dwInUcastPkts: longint;
dwInNUcastPkts: longint;
dwInDiscards: longint;
dwInErrors: longint;
dwInUnknownProtos: longint;
dwOutOctets: longint;
dwOutUcastPkts: longint;
dwOutNUcastPkts: longint;
dwOutDiscards: longint;
dwOutErrors: longint;
dwOutQLen: longint;
dwDescrLen: longint;
bDescr: string;
sIpAddress: string;
sIpMask: string;
end;
function Get_EthernetAdapterDetail(var AdapterDataFound: TAdapterInfo): boolean;
var
pIfTable: ^_IfTable;
pIpTable: ^_IpAddrTable;
ifTableSize, ipTableSize: longint;
tmp: string;
i, j, k, m: integer;
ErrCode: longint;
sAddr, sMask: in_addr;
IPAddresses, IPMasks: TStringList;
sIPAddressLine, sIPMaskLine: string;
bResult: boolean;
begin
bResult := True; //default return value
pIfTable := nil;
pIpTable := nil;
IPAddresses := TStringList.Create;
IPMasks := TStringList.Create;
try
// First: just get the buffer size.
// TableSize returns the size needed.
ifTableSize := 0; // Set to zero so the GetIfTabel function
// won't try to fill the buffer yet,
// but only return the actual size it needs.
GetIfTable(pIfTable, ifTableSize, 1);
if (ifTableSize < SizeOf(MIB_IFROW) + Sizeof(longint)) then
begin
bResult := False;
Result := bResult;
Exit; // less than 1 table entry?!
end;
ipTableSize := 0;
GetIpAddrTable(pIpTable, ipTableSize, 1);
if (ipTableSize < SizeOf(MIB_IPADDRROW) + Sizeof(longint)) then
begin
bResult := False;
Result := bResult;
Exit; // less than 1 table entry?!
end;
// Second:
// allocate memory for the buffer and retrieve the
// entire table.
GetMem(pIfTable, ifTableSize);
ErrCode := GetIfTable(pIfTable, ifTableSize, 1);
if ErrCode <> ERROR_SUCCESS then
begin
bResult := False;
Result := bResult;
Exit; // OK, that did not work.
// Not enough memory i guess.
end;
GetMem(pIpTable, ipTableSize);
ErrCode := GetIpAddrTable(pIpTable, ipTableSize, 1);
if ErrCode <> ERROR_SUCCESS then
begin
bResult := False;
Result := bResult;
Exit;
end;
for k := 1 to pIpTable^.dwNumEntries do
begin
sAddr.S_addr := pIpTable^.table[k].dwAddr;
sMask.S_addr := pIpTable^.table[k].dwMask;
sIPAddressLine := Format('0x%8.8x', [(pIpTable^.table[k].dwIndex)]) +
'=' + Format('%s', [inet_ntoa(sAddr)]);
sIPMaskLine := Format('0x%8.8x', [(pIpTable^.table[k].dwIndex)]) +
'=' + Format('%s', [inet_ntoa(sMask)]);
IPAddresses.Add(sIPAddressLine);
IPMasks.Add(sIPMaskLine);
end;
SetLength(AdapterDataFound, pIfTable^.nRows); //initialize the array or records
for i := 1 to pIfTable^.nRows do
try
//if pIfTable^.ifRow[i].dwType=MIB_IF_TYPE_ETHERNET then
//begin
m := i - 1;
AdapterDataFound[m].dwIndex := 4;//(pIfTable^.ifRow[i].dwIndex);
AdapterDataFound[m].dwType := (pIfTable^.ifRow[i].dwType);
AdapterDataFound[m].dwIndex := (pIfTable^.ifRow[i].dwIndex);
AdapterDataFound[m].sIpAddress :=
IPAddresses.Values[Format('0x%8.8x', [(pIfTable^.ifRow[i].dwIndex)])];
AdapterDataFound[m].sIpMask :=
IPMasks.Values[Format('0x%8.8x', [(pIfTable^.ifRow[i].dwIndex)])];
AdapterDataFound[m].dwMtu := (pIfTable^.ifRow[i].dwMtu);
AdapterDataFound[m].dwSpeed := (pIfTable^.ifRow[i].dwSpeed);
AdapterDataFound[m].dwAdminStatus := (pIfTable^.ifRow[i].dwAdminStatus);
AdapterDataFound[m].dwOperStatus := (pIfTable^.ifRow[i].dwOperStatus);
AdapterDataFound[m].dwInUcastPkts := (pIfTable^.ifRow[i].dwInUcastPkts);
AdapterDataFound[m].dwInNUcastPkts := (pIfTable^.ifRow[i].dwInNUcastPkts);
AdapterDataFound[m].dwInDiscards := (pIfTable^.ifRow[i].dwInDiscards);
AdapterDataFound[m].dwInErrors := (pIfTable^.ifRow[i].dwInErrors);
AdapterDataFound[m].dwInUnknownProtos := (pIfTable^.ifRow[i].dwInUnknownProtos);
AdapterDataFound[m].dwOutNUcastPkts := (pIfTable^.ifRow[i].dwOutNUcastPkts);
AdapterDataFound[m].dwOutUcastPkts := (pIfTable^.ifRow[i].dwOutUcastPkts);
AdapterDataFound[m].dwOutDiscards := (pIfTable^.ifRow[i].dwOutDiscards);
AdapterDataFound[m].dwOutErrors := (pIfTable^.ifRow[i].dwOutErrors);
AdapterDataFound[m].dwOutQLen := (pIfTable^.ifRow[i].dwOutQLen);
AdapterDataFound[m].bDescr := (pIfTable^.ifRow[i].bDescr);
tmp := '';
for j := 0 to pIfTable^.ifRow[i].dwPhysAddrLen - 1 do
begin
if Length(tmp) > 0 then
tmp := tmp + '-' + format('%.2x', [pIfTable^.ifRow[i].bPhysAddr[j]])
else
tmp := tmp + format('%.2x', [pIfTable^.ifRow[i].bPhysAddr[j]]);
end;
if Length(tmp) > 0 then
begin
AdapterDataFound[m].bPhysAddr := tmp;
end;
except
bResult := False;
Result := bResult;
Exit;
end;
finally
if Assigned(pIfTable) then
begin
FreeMem(pIfTable, ifTableSize);
end;
FreeAndNil(IPMasks);
FreeAndNil(IPAddresses);
end;
Result := bResult;
end;
var
AdapterData: TAdapterInfo;
i: integer;
begin
try
WriteLn('');
if Get_EthernetAdapterDetail(AdapterData) then
begin
for i := 0 to Length(AdapterData) - 1 do
begin
WriteLn(Format('0x%8.8x', [AdapterData[i].dwIndex]));
WriteLn('"' + AdapterData[i].bDescr + '"');
Write(Format(#9 + 'Link encap: %s ', [Get_if_type(AdapterData[i].dwType)]));
if Length(AdapterData[i].bPhysAddr) > 0 then
Write('HWaddr: ' + AdapterData[i].bPhysAddr);
Write(#13 + #10 + #9 + 'inet addr:' + AdapterData[i].sIpAddress);
WriteLn(' Mask: ' + AdapterData[i].sIpMask);
WriteLn(Format(#9 + 'MTU: %d Speed:%.2f Mbps', [AdapterData[i].dwMtu,
(AdapterData[i].dwSpeed) / 1000 / 1000]));
Write(#9 + 'Admin status:' + Get_if_admin_status(AdapterData[i].dwAdminStatus));
WriteLn(' Oper status:' + Get_if_oper_status(AdapterData[i].dwOperStatus));
WriteLn(#9 + Format('RX packets:%d dropped:%d errors:%d unkown:%d',
[AdapterData[i].dwInUcastPkts + AdapterData[i].dwInNUcastPkts,
AdapterData[i].dwInDiscards, AdapterData[i].dwInErrors,
AdapterData[i].dwInUnknownProtos]));
WriteLn(#9 + Format('TX packets:%d dropped:%d errors:%d txqueuelen:%d',
[AdapterData[i].dwOutUcastPkts + AdapterData[i].dwOutNUcastPkts,
AdapterData[i].dwOutDiscards, AdapterData[i].dwOutErrors,
AdapterData[i].dwOutQLen]));
WriteLn('');
end;
end
else
begin
WriteLn(#13+#10+'*** Error retrieving adapter information');
end;
except
on E: Exception do
Writeln(E.ClassName, ': ', E.Message);
end;
end.