Technical Q&A NW41

Gestalt Selectors for Macintosh Networking

Q: What are the different Gestalt selectors for Macintosh networking?

A: Here is the breakdown:

MacTCP

• MacTCP versions 1.0 through 1.0.3 did not register this selector.
• MacTCP version 1.1 returns a value of 1.
• MacTCP version 1.1.1 returns a value of 2.
• MacTCP version 2.0 returns a value of 3.

A value of 0 is returned if the driver is not opened.

AppleTalk

The Gestalt selectors for AppleTalk are 'atkv' and 'atlk'.

The 'atlk' Gestalt selector was introduced in AppleTalk version 54 to provide basic version information. Calling Gestalt with the 'atlk' selector provides the major revision version in the low-order byte of the function result. For example, passing the 'atlk' selector in a Gestalt call or through MacsBuG with a result of 0x0000003C means that AppleTalk version 60 is present. (Please note that the 'atlk' selector is not available when AppleTalk is turned off in the Chooser.)

The 'atkv' Gestalt selector was introduced as an alternative in AppleTalk version 56 to provide more complete version information via the 'vers' resource. For example, passing the 'atkv' selector to AppleTalk version 60 through a Gestalt call or MacsBuG yields the following LONGINT result: 0x3C108000.

Open Transport

The Gestalt selectors for Open Transport are 'otan' and 'otvr'. You can test whether Open Transport and its various parts are available by using the Gestalt function with the 'otan' selector. The bits currently used are defined by constants, defined in OpenTransport.h and shown below.

enum {
        gestaltOpenTpt                   = 'otan',
        gestaltOpenTptPresent           = 0x00000001,
        gestaltOpenTptLoaded            = 0x00000002,
        gestaltOpenTptAppleTalkPresent  = 0x00000004,
        gestaltOpenTptAppleTalkLoaded   = 0x00000008,
        gestaltOpenTptTCPPresent        = 0x00000010,
        gestaltOpenTptTCPLoaded         = 0x00000020,
        gestaltOpenTptNetwarePresent    = 0x00000040,
        gestaltOpenTptNetwareLoaded     = 0x00000080
};

If Gestalt returns no error and responds with a non-zero value, Open Transport is available. To find out whether OT, AppleTalk, TCP, or NetWare are present, you can examine the response parameter bits as shown above. For example, passing the 'otan' selector in a Gestalt call or through MacsBuG with a result of 0x0000001F means that the Open Transport is present and loaded, AppleTalk driver is also present and loaded, and MacTCP is present but NOT loaded.

The 'otvr' selector is used to determine the Open Transport Version in NumVersion format. For example, passing the 'otvr' selector through a Gestalt call or MacsBuG to OT version 1.1.1b9 yields the following LONGINT result: 0x01116009. (Note that OT versions 1.0 through 1.0.8 did not register this selector.) For more information on Apple's Version Numbering Scheme and NumVersion format, please see Technote OV12:Version Territory.

Open Transport / PPP

The Gestalt selectors for Open Transport / PPP are 'otra' and 'otrv'. You can test whether Open Transport / PPP and its various parts are available by using the Gestalt function with the 'otra' selector. The bits currently used are defined by constants, defined in OpenTptPPP.h check OT/PPP SDK and shown below.

enum {
        gestaltOpenTptRemoteAccess      = 'otra',
        gestaltOpenTptRemoteAccessPresent       = 0x00000000,
        gestaltOpenTptRemoteAccessLoaded        = 0x00000001,
        gestaltOpenTptRemoteAccessClientOnly    = 0x00000002,
        gestaltOpenTptRemoteAccessPServer       = 0x00000003,
        gestaltOpenTptRemoteAccessMPServer      = 0x00000004,
        gestaltOpenTptPPPPresent                = 0x00000005,
        gestaltOpenTptARAPPresent               = 0x00000006
 };

More information on accessing using the Open Transport / PPP API is available in the Open Transport documentation.

Open Transport / Modem

The Gestalt selectors for Open Transport/Modem are 'otmo' and 'otmv'. You can test whether Open Transport/ Modem and its various parts are available by using the Gestalt function with the 'otmo' selector.

enum {
        gestaltOpenTptModem         = 'otmo',
        gestaltOpenTptModemPresent      = 0x00000000
 };