Re: Reading names of comports [COM1, COM2 etc]

Hello Vic,

Vic Fraenckel schrieb:
I am attempting to read the names of the known com ports on my computer using the following function.

as You see, You dived into a "not simple" problem.
First:
Dealing with the StringList and the Registry is described in the other postings, so I leave You alone with this :-)
Second:
While all Comports are in the "HARDWARE\DEVICEMAP\SERIALCOMM" key under NT/2K/XP they are under a different location under 9x/ME. Harder, under 9x/ME, finally a lot of Keys must be scanned to find virtual Modems creating there own commports.
There might be also the possibility that a commport exists, but is not in the registry. I have never seen this behaviour but I have heard about. Probably than is seems to be usefull to probe commport names like "COM1"... if they exists. The problem there is that the createfile fill fail either on non exixting ports or if the port is allready in use.

I use the function below, (could also found in my OpenSource SerialNG component http://www.domis.de/serialng.htm in the file "CommPortList.pas"), which scans the registry only and do no probing. I found that this works well on all systems, that I have used so far.

Best regards
Ekkehard Domning


procedure GetPortList(Strings : TStrings);
var Reg : TRegistry;

  procedure ScanRegHardware;
  var
    i : integer;
    PortName : string;
    LName : TStringList;
  begin
    if Reg.OpenKeyReadOnly('\hardware\devicemap\serialcomm') then
      begin
        LName := TStringList.Create;
        Reg.GetValueNames(LName);
        for i := 0 to LName.Count - 1 do
          begin
            if Reg.GetDataType(LName.Strings[i]) = rdString then
              begin
                PortName := Reg.ReadString(LName.Strings[i]);
                if Strings.IndexOf(PortName) < 0 then
                  Strings.Add(PortName);
              end
          end;
        LName.Free;
      end
  end;

procedure ScanRegEnum(Key : String);
// This Subprocedure recurses thru all keys below key
var
LKey : TStringList;
LName : TStringList;
i : Integer;
Driver, PortName : String;
PortSubClass : Byte;
begin
if not Reg.OpenKeyReadOnly(Key) then // Danke Andreas Schmidt!
Exit;
LName := TStringList.Create;
Reg.GetValueNames(LName);
i := LName.IndexOf('class');
if i >= 0 then
begin
if (Reg.GetDataType('class') = rdString) and
((LowerCase(Reg.ReadString('class')) = 'ports') or //normal Serialports like COMx
(LowerCase(Reg.ReadString('class')) = 'modem')) and //some abnormal onboard Modems
(Reg.GetDataType('driver') = rdString) and
(Reg.GetDataType('portname') = rdString) then
begin
Driver := Reg.ReadString('driver');
PortName := Reg.ReadString('portname');
if Reg.OpenKeyReadOnly('\System\CurrentControlSet\Services\Class\'+ Driver) and
(Reg.ReadBinaryData('PortSubClass',PortSubClass,1) = 1) and
((PortSubClass = 1) or //Ports
(PortSubClass = 2)) and //Modems
(Strings.IndexOf(PortName) < 0) then
Strings.Add(PortName);
end
end;
LName.Free;
Reg.OpenKeyReadOnly(Key);
if Reg.HasSubKeys then
begin
LKey := TStringList.Create;
Reg.GetKeyNames(LKey);
for i := 0 to LKey.Count - 1 do
begin
ScanRegEnum(Key + '\' + LKey[i]);
end;
LKey.Free;
end;
end;

var
  VersionInfo : TOSVersionInfo;
begin
  if CheckOS(VersionInfo) > 0 then
    if VersionInfo.dwMajorVersion >= 4 then
      begin
        Reg := TRegistry.Create;
        Reg.RootKey := HKEY_LOCAL_MACHINE;
        if VersionInfo.dwMajorVersion > 4 then
          ScanRegHardware //Win 2k, XP
        else if VersionInfo.dwMinorVersion > 0 then
          ScanRegEnum('\enum') //Win9x, mE
        else
          ScanRegHardware; //WinNT
        Reg.Free;
      end;
end;

the code uses also a function for OS determination

function CheckOS(var VersionInfo : TOSVersionInfo) : Integer;
begin
{
dwOSVersionInfoSize: DWORD;
dwMajorVersion: DWORD;
dwMinorVersion: DWORD;
dwBuildNumber: DWORD;
dwPlatformId: DWORD;
szCSDVersion: array[0..127] of AnsiChar; // Maintenance string for PSS usage
}
VersionInfo.dwOSVersionInfoSize := SizeOf(VersionInfo);
if GetVersionEx(VersionInfo) then
CheckOS := VersionInfo.dwPlatformId
else
CheckOS := -1;
end;
.

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