docs: document legacy direct NCP utility layouts

TODO.md

@@ -123,6 +123,13 @@ Current status:
   Set` are implemented, but the SDK request contains a `LockFlag` byte that
   the current code does not read.  This parser difference is documented inline
   but not changed yet.
+- `NCP 0x12 Get Volume Info with Number`, `NCP 0x13 Get Station Number`,
+  `NCP 0x14 Get File Server Date And Time`, and the `NCP 0x15` message group
+  handoff now have inline SDK request/reply layout documentation.
+- `NCP 0x13 Get Station Number` is documented by the SDK as a three-byte
+  StationNumber reply; MARS-NWE currently returns only the low one-byte
+  connection number.  This parser/reply difference is documented inline but not
+  changed yet.
 
 Follow-up:
 
@@ -141,6 +148,8 @@ Follow-up:
   evidence is available.
 - Decide whether `0x0d` and `0x0e` should consume or ignore the documented
   `LockFlag` byte after direct requester evidence is available.
+- Verify whether the current one-byte `0x13` reply is required by old clients
+  or whether the SDK three-byte StationNumber reply should be implemented.
 - Verify the implemented file/logical-record/physical-record calls against the
   Novell SDK request/reply layouts and a real DOS requester or direct test
   caller.

src/nwconn.c

@@ -3082,6 +3082,29 @@ static int handle_ncp_serv(void)
       break;
 
       case 0x12 : { /* Get Volume Info with Number */
+        /*
+         * NCP 0x2222/18 Get Volume Info with Number returns the legacy
+         * NetWare 2.x/3.x volume-space summary for a numeric volume id.
+         *
+         * SDK request:
+         *
+         *   byte  VolumeNumber
+         *
+         * SDK reply:
+         *
+         *   word  SectorsPerCluster       (Hi-Lo)
+         *   word  TotalVolumeClusters     (Hi-Lo)
+         *   word  AvailableClusters       (Hi-Lo)
+         *   word  TotalDirectorySlots     (Hi-Lo)
+         *   word  AvailableDirectorySlots (Hi-Lo)
+         *   byte  VolumeName[16]
+         *   word  RemovableFlag           (Hi-Lo)
+         *
+         * SDK completion: 0x00 success, 0x98 disk map error.
+         *
+         * MARS-NWE reads the one-byte VolumeNumber from requestdata[0]
+         * and builds the documented fixed-size reply.
+         */
         int volume = (int)*requestdata;
         struct XDATA {
           uint8 sec_per_block[2];
@@ -3119,11 +3142,22 @@ static int handle_ncp_serv(void)
 
       case 0x13 : { /* Get Station Number */
         /*
-         * This is the old one-byte connection number call used by
-         * DOS requesters before the richer NCP 23 connection services.
-         * The SDK describes the client-visible API as
-         * NWGetConnectionNumber(); older low-level documentation names the
-         * underlying simple NCP 0x13 "Get Station Number".
+         * NCP 0x2222/19 Get Station Number returns the calling station's
+         * legacy connection/station number.
+         *
+         * SDK request: no payload after FunctionCode (19).
+         *
+         * SDK reply:
+         *
+         *   byte  StationNumber[3]
+         *
+         * SDK completion: 0x00 success.
+         *
+         * MARS-NWE currently returns the low one-byte connection number only,
+         * which matches the source's long-standing old-client compatibility
+         * behaviour but is narrower than the three-byte SDK reply layout.
+         * This documentation patch records that difference only; endpoint
+         * behaviour is intentionally unchanged here.
          */
         if (act_connection > 0 && act_connection < 256) {
           *responsedata=(uint8) act_connection;
@@ -3136,7 +3170,27 @@ static int handle_ncp_serv(void)
       } 
       break;
 
-      case 0x14 : { /* GET DATE und TIME */
+      case 0x14 : { /* Get File Server Date And Time */
+        /*
+         * NCP 0x2222/20 Get File Server Date And Time returns the server
+         * clock in the old fixed seven-byte format.
+         *
+         * SDK request: no payload after FunctionCode (20).
+         *
+         * SDK reply:
+         *
+         *   byte  Year       (80..99 => 1980..1999, 100..179 => 2000..2079)
+         *   byte  Month      (1..12)
+         *   byte  Day        (1..31)
+         *   byte  Hour       (0..23)
+         *   byte  Minute     (0..59)
+         *   byte  Second     (0..59)
+         *   byte  DayOfWeek  (0 = Sunday)
+         *
+         * SDK completion: 0x00 success.
+         *
+         * MARS-NWE builds the documented seven-byte reply from localtime().
+         */
         struct SERVER_DATE {
           uint8   year;
           uint8   mon;
@@ -3163,6 +3217,20 @@ static int handle_ncp_serv(void)
       break;
 
       case 0x15 :
+        /*
+         * NCP 0x2222/21 is the Message NCP function group.  The SDK routes
+         * individual message calls through a nested SubFunctionCode, for
+         * example old broadcast send/get calls and newer connection-message
+         * control calls.
+         *
+         * SDK group request header:
+         *
+         *   word  SubFuncStrucLen (Hi-Lo)
+         *   byte  SubFunctionCode
+         *   ...   subfunction-specific payload
+         *
+         * This direct dispatcher deliberately leaves the group to nwbind.
+         */
         return(-1); /* nwbind must do this call */
 
       case 0x16 : {