Take serial numbers from a pool the whole entry shares

Each station worked out its next number as the highest in its log plus one,
so two operators typing at the same moment both sent the same number and
one of the two contacts was wrong in the sponsor's log.

SerialNumberPool holds the highest number taken per band, which is N1MM's
QSONumbers array. A number is taken at the first character of the callsign,
as N1MM takes it, and ReserveNr tells the other stations before the contact
is worked. A number at or below one this station has used is answered with
the whole pool, N1MM's QSONRS, and the station that is behind counts on from
there. The pool also goes out when a contest is opened and when the numbers
are started again.

Contest.NumbersByBand says whether the numbers run per band or as one
sequence for the station. CQ WPX runs one per band for a multi-two and a
multi-multi; every other contest here runs one sequence. The band index in
the message is N1MM's, so the array lines up with theirs.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015NZkFxHde1iifAQemFTHxf

src/Nonemm.Network/StationLink.cs

@@ -131,6 +131,14 @@ public sealed class StationLink : IDisposable
     /// owner is told and does it.
     public event EventHandler? SerialNumbersReset;
 
+    /// A serial number another station has taken, with the frequency it took
+    /// it on. The pool is not the link's, so the owner is told and notes it.
+    public event EventHandler<ReservedNumberMessage>? NumberReserved;
+
+    /// The whole serial number pool from another station, one number per band
+    /// in N1MM's band order.
+    public event EventHandler<IReadOnlyList<int>>? SerialNumbersArrived;
+
     /// A callsign another station handed to this one's call stack, with the
     /// contact behind it when there was one.
     public event EventHandler<StackedCall>? CallStacked;
@@ -424,6 +432,30 @@ public sealed class StationLink : IDisposable
         StationsChanged?.Invoke(this, EventArgs.Empty);
     }
 
+    /// Says which serial number this station has taken for the contact it is
+    /// about to work. It goes out at the first character of the callsign, so
+    /// the other operators' next number is above this one.
+    public Task<int> SendReservedNumberAsync(
+        int number,
+        Frequency frequency,
+        CancellationToken cancellation = default) =>
+        SendAsync(
+            StationMessages.ReserveNumber(number, frequency, StationNumber, computerName),
+            cancellation);
+
+    /// Sends the whole pool, which is what a station answers with when the
+    /// number another one has taken is one this station has already used.
+    public Task<int> SendSerialNumbersAsync(
+        IReadOnlyList<int> numbers,
+        CancellationToken cancellation = default) =>
+        SendAsync(
+            StationMessages.SerialNumbers(
+                Log?.ContestName ?? "",
+                numbers,
+                StationNumber,
+                computerName),
+            cancellation);
+
     /// Tells every station to start its serial numbers again at one.
     public Task<int> SendResetSerialNumbersAsync(CancellationToken cancellation = default) =>
         SendAsync(StationMessages.ResetSerialNumbers(StationNumber, computerName), cancellation);
@@ -893,6 +925,21 @@ public sealed class StationLink : IDisposable
             case "RESETQSONRS":
                 SerialNumbersReset?.Invoke(this, EventArgs.Empty);
                 break;
+            case "RESERVENR":
+                NumberReserved?.Invoke(
+                    this,
+                    new ReservedNumberMessage(
+                        record.Number(0),
+                        Frequency.FromKilohertz(record.Decimal(1) / 100)));
+                break;
+            case "QSONRS":
+                // the pool is per contest, so a station logging another one is
+                // counting something else
+                if (Log is null || record.Field(0).Equals(Log.ContestName, StringComparison.OrdinalIgnoreCase))
+                {
+                    SerialNumbersArrived?.Invoke(this, StationMessages.ReadSerialNumbers(record));
+                }
+                break;
             case "STACKANOTHERCALL":
                 CallStacked?.Invoke(this, new StackedCall(record.Field(0), null, station.ComputerName));
                 break;