feat(batch45): implement events server methods — stats, remote tracking, connection events

Port 80 features from server/events.go including the full events infrastructure:
internal send/receive loops, system subscription machinery, statsz heartbeats,
remote server tracking, connection event advisories, user-info handler, OCSP peer
reject events, remote latency merge, kick/ldm client, and helper functions.

Add ClearConnectionHeartbeatTimer/SetConnectionHeartbeatTimer to Account,
add MsgHandler/SysMsgHandler delegates and supporting types (ServerApiResponse,
EventFilterOptions, StatszEventOptions, UserInfo, KickClientReq, LdmClientReq,
AccNumSubsReq) to EventTypes.cs, and add Seq field to ServerInfo for heartbeat
sequence tracking.

dotnet/src/ZB.MOM.NatsNet.Server/Accounts/Account.cs

@@ -4507,6 +4507,28 @@ public sealed partial class Account : INatsAccount
         return string.Empty;
     }
 
+    /// <summary>
+    /// Clears the connection-heartbeat timer. Caller must hold the account lock.
+    /// Mirrors Go <c>(a *Account) clearConnectionTimer()</c> in server/events.go.
+    /// </summary>
+    internal void ClearConnectionHeartbeatTimer()
+    {
+        ClearTimerLocked(ref _ctmr);
+    }
+
+    /// <summary>
+    /// Starts or resets the connection-heartbeat timer.
+    /// Caller must hold the account lock.
+    /// Mirrors Go inline timer setup in <c>sendAccConnsUpdate()</c>.
+    /// </summary>
+    internal void SetConnectionHeartbeatTimer(long delayMs, Action callback)
+    {
+        if (_ctmr == null)
+            _ctmr = new Timer(_ => callback(), null, delayMs, Timeout.Infinite);
+        else
+            _ctmr.Change(delayMs, Timeout.Infinite);
+    }
+
     /// <summary>
     /// Stops and nulls out a timer. Lock must be held by the caller.
     /// Mirrors Go <c>clearTimer(t **time.Timer)</c>.

dotnet/src/ZB.MOM.NatsNet.Server/Events/EventHelpers.cs

@@ -0,0 +1,82 @@
+// Copyright 2018-2026 The NATS Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Adapted from server/events.go (package-level helpers) in the NATS server Go source.
+
+namespace ZB.MOM.NatsNet.Server;
+
+/// <summary>
+/// Package-level helper functions used by the events subsystem.
+/// Mirrors Go package-level functions in server/events.go.
+/// </summary>
+internal static class EventHelpers
+{
+    // =========================================================================
+    // accForClient — mirrors Go accForClient
+    // =========================================================================
+
+    /// <summary>
+    /// Returns the account name for the given client connection.
+    /// Mirrors Go <c>accForClient(c *client) string</c> in server/events.go.
+    /// </summary>
+    internal static string AccForClient(ClientConnection c)
+    {
+        var acc = c._account as Account;
+        return acc?.Name ?? "N/A";
+    }
+
+    // =========================================================================
+    // issuerForClient — mirrors Go issuerForClient
+    // =========================================================================
+
+    /// <summary>
+    /// Returns the issuer key for the given client connection.
+    /// In Go this inspects c.user.SigningKey / c.user.Account.Name.
+    /// In .NET the NkeyUser signing key is not stored on ClientConnection;
+    /// we return an empty string (same as Go when c.user == nil).
+    /// Mirrors Go <c>issuerForClient(c *client) string</c> in server/events.go.
+    /// </summary>
+    internal static string IssuerForClient(ClientConnection c)
+    {
+        // ClientConnection does not expose a stored User/NkeyUser reference
+        // with a SigningKey after registration.  Return empty (safe default).
+        return string.Empty;
+    }
+
+    // =========================================================================
+    // respondToUpdate — mirrors Go respondToUpdate
+    // =========================================================================
+
+    /// <summary>
+    /// Sends an account JWT update response back to the requesting server.
+    /// Mirrors Go <c>respondToUpdate(s *Server, respSubj, acc, message string, err error)</c>
+    /// in server/accounts.go (called from events.go).
+    /// </summary>
+    internal static void RespondToUpdate(NatsServer s, string respSubj, string acc, string message, Exception? err)
+    {
+        if (string.IsNullOrEmpty(respSubj))
+            return;
+
+        string response;
+        if (err != null)
+            response = string.IsNullOrEmpty(acc)
+                ? $"{message}: {err.Message}"
+                : $"[{acc}] {message}: {err.Message}";
+        else
+            response = string.IsNullOrEmpty(acc)
+                ? message
+                : $"[{acc}] {message}";
+
+        s.SendInternalMsg(respSubj, string.Empty, null, response);
+    }
+}

dotnet/src/ZB.MOM.NatsNet.Server/Events/EventTypes.cs

@@ -151,13 +151,212 @@ public static class EventIntervals
 /// </summary>
 public delegate void SysMsgHandler(
     Subscription sub,
-    NatsClient client,
+    ClientConnection client,
     Account acc,
     string subject,
     string reply,
     byte[] hdr,
     byte[] msg);
 
+// ============================================================================
+// MsgHandler — subscription message callback delegate
+// Mirrors Go <c>msgHandler</c> func type in server/events.go.
+// ============================================================================
+
+/// <summary>
+/// Callback for a subscription message. Identical signature to
+/// <see cref="SysMsgHandler"/>; the distinction exists in Go but is
+/// collapsed here since both carry the same parameters.
+/// Mirrors Go <c>msgHandler</c> in server/events.go.
+/// </summary>
+public delegate void MsgHandler(
+    Subscription sub,
+    ClientConnection client,
+    Account acc,
+    string subject,
+    string reply,
+    byte[] hdr,
+    byte[] msg);
+
+// ============================================================================
+// ServerApiError — error payload for server API responses
+// Mirrors Go <c>ApiError</c> used in server/events.go responses.
+// ============================================================================
+
+/// <summary>
+/// Error payload returned in <see cref="ServerApiResponse"/> when a
+/// monitoring z-endpoint request fails.
+/// Mirrors Go <c>ApiError</c> struct used by server API responses.
+/// </summary>
+public sealed class ServerApiError
+{
+    [System.Text.Json.Serialization.JsonPropertyName("code")]
+    public int Code { get; set; }
+
+    [System.Text.Json.Serialization.JsonPropertyName("description")]
+    public string Description { get; set; } = string.Empty;
+}
+
+// ============================================================================
+// ServerApiResponse — wrapper for server API (z-endpoint) responses
+// Mirrors Go <c>ServerAPIResponse</c> in server/events.go.
+// ============================================================================
+
+/// <summary>
+/// Standard envelope returned by server monitoring API (varz, connz, etc.)
+/// published via the internal system bus.
+/// Mirrors Go <c>ServerAPIResponse</c> in server/events.go.
+/// </summary>
+public sealed class ServerApiResponse
+{
+    [System.Text.Json.Serialization.JsonPropertyName("server")]
+    public ServerInfo? Server { get; set; }
+
+    [System.Text.Json.Serialization.JsonPropertyName("data")]
+    [System.Text.Json.Serialization.JsonIgnore(Condition = System.Text.Json.Serialization.JsonIgnoreCondition.WhenWritingNull)]
+    public object? Data { get; set; }
+
+    [System.Text.Json.Serialization.JsonPropertyName("error")]
+    [System.Text.Json.Serialization.JsonIgnore(Condition = System.Text.Json.Serialization.JsonIgnoreCondition.WhenWritingNull)]
+    public ServerApiError? Error { get; set; }
+}
+
+// ============================================================================
+// EventFilterOptions — server filter options for z-endpoint requests
+// Mirrors Go <c>EventFilterOptions</c> in server/events.go.
+// ============================================================================
+
+/// <summary>
+/// Filter parameters sent in monitoring z-endpoint request messages that
+/// allow targeting a specific server, cluster, or set of tags.
+/// Mirrors Go <c>EventFilterOptions</c> in server/events.go.
+/// </summary>
+public class EventFilterOptions
+{
+    [System.Text.Json.Serialization.JsonPropertyName("server_name")]
+    [System.Text.Json.Serialization.JsonIgnore(Condition = System.Text.Json.Serialization.JsonIgnoreCondition.WhenWritingNull)]
+    public string? Name { get; set; }
+
+    [System.Text.Json.Serialization.JsonPropertyName("cluster")]
+    [System.Text.Json.Serialization.JsonIgnore(Condition = System.Text.Json.Serialization.JsonIgnoreCondition.WhenWritingNull)]
+    public string? Cluster { get; set; }
+
+    [System.Text.Json.Serialization.JsonPropertyName("host")]
+    [System.Text.Json.Serialization.JsonIgnore(Condition = System.Text.Json.Serialization.JsonIgnoreCondition.WhenWritingNull)]
+    public string? Host { get; set; }
+
+    [System.Text.Json.Serialization.JsonPropertyName("domain")]
+    [System.Text.Json.Serialization.JsonIgnore(Condition = System.Text.Json.Serialization.JsonIgnoreCondition.WhenWritingNull)]
+    public string? Domain { get; set; }
+
+    [System.Text.Json.Serialization.JsonPropertyName("tags")]
+    [System.Text.Json.Serialization.JsonIgnore(Condition = System.Text.Json.Serialization.JsonIgnoreCondition.WhenWritingNull)]
+    public List<string>? Tags { get; set; }
+
+    /// <summary>
+    /// When true, name/cluster/host must match exactly; when false, substring
+    /// matching is used.
+    /// Mirrors Go <c>EventFilterOptions.ExactMatch</c>.
+    /// </summary>
+    [System.Text.Json.Serialization.JsonPropertyName("exact")]
+    public bool ExactMatch { get; set; }
+}
+
+// ============================================================================
+// UserInfo — user info response payload for $SYS.REQ.USER.INFO
+// Mirrors Go <c>UserInfo</c> struct in server/events.go.
+// ============================================================================
+
+/// <summary>
+/// Response payload returned by the <c>$SYS.REQ.USER.INFO</c> endpoint.
+/// Contains the authenticated user's identity, account, permissions, and
+/// claim expiry.
+/// Mirrors Go <c>UserInfo</c> struct in server/events.go.
+/// </summary>
+public sealed class UserInfo
+{
+    [System.Text.Json.Serialization.JsonPropertyName("userId")]
+    public string UserId { get; set; } = string.Empty;
+
+    [System.Text.Json.Serialization.JsonPropertyName("account")]
+    public string Account { get; set; } = string.Empty;
+
+    [System.Text.Json.Serialization.JsonPropertyName("permissions")]
+    [System.Text.Json.Serialization.JsonIgnore(Condition = System.Text.Json.Serialization.JsonIgnoreCondition.WhenWritingNull)]
+    public object? Permissions { get; set; }
+
+    [System.Text.Json.Serialization.JsonPropertyName("expires")]
+    [System.Text.Json.Serialization.JsonIgnore(Condition = System.Text.Json.Serialization.JsonIgnoreCondition.WhenWritingDefault)]
+    public DateTime Expires { get; set; }
+}
+
+// ============================================================================
+// KickClientReq / LdmClientReq — client control request payloads
+// Mirrors Go anonymous structs used in server/events.go.
+// ============================================================================
+
+/// <summary>
+/// Request payload for <c>$SYS.REQ.SERVER.{id}.KICK</c>, which asks this
+/// server to forcefully disconnect the client with the given CID.
+/// Mirrors the anonymous struct used in <c>Server.kickClient()</c>.
+/// </summary>
+internal sealed class KickClientReq
+{
+    [System.Text.Json.Serialization.JsonPropertyName("cid")]
+    public ulong Cid { get; set; }
+}
+
+/// <summary>
+/// Request payload for <c>$SYS.REQ.SERVER.{id}.LDM</c>, which asks this
+/// server to put the client with the given CID into lame-duck mode.
+/// Mirrors the anonymous struct used in <c>Server.ldmClient()</c>.
+/// </summary>
+internal sealed class LdmClientReq
+{
+    [System.Text.Json.Serialization.JsonPropertyName("cid")]
+    public ulong Cid { get; set; }
+}
+
+// ============================================================================
+// StatszEventOptions — options for statsz z-endpoint requests
+// Mirrors Go <c>StatszEventOptions</c> in server/events.go.
+// ============================================================================
+
+/// <summary>
+/// Options embedded in z-endpoint request messages that allow filtering and
+/// configuring the statsz response.
+/// Mirrors Go <c>StatszEventOptions</c> in server/events.go.
+/// </summary>
+public sealed class StatszEventOptions : EventFilterOptions
+{
+}
+
+// ============================================================================
+// AccNumSubsReq — request payload for subscription count queries
+// Mirrors Go <c>accNumSubsReq</c> struct in server/events.go.
+// ============================================================================
+
+/// <summary>
+/// Payload for <c>$SYS.REQ.ACCOUNT.NSUBS</c> requests, which ask a remote
+/// server how many local subscriptions exist for a given account + subject.
+/// Mirrors Go <c>accNumSubsReq</c> in server/events.go.
+/// </summary>
+internal sealed class AccNumSubsReq
+{
+    [System.Text.Json.Serialization.JsonPropertyName("server")]
+    public ServerInfo Server { get; set; } = new();
+
+    [System.Text.Json.Serialization.JsonPropertyName("acc")]
+    public string Account { get; set; } = string.Empty;
+
+    [System.Text.Json.Serialization.JsonPropertyName("subject")]
+    public string Subject { get; set; } = string.Empty;
+
+    [System.Text.Json.Serialization.JsonPropertyName("queue")]
+    [System.Text.Json.Serialization.JsonIgnore(Condition = System.Text.Json.Serialization.JsonIgnoreCondition.WhenWritingNull)]
+    public string? Queue { get; set; }
+}
+
 // ============================================================================
 // InSysMsg — queued internal system message
 // Mirrors Go <c>inSysMsg</c> struct in server/events.go.
@@ -170,9 +369,9 @@ public delegate void SysMsgHandler(
 /// </summary>
 internal sealed class InSysMsg
 {
-    public Subscription?  Sub     { get; set; }
-    public NatsClient?    Client  { get; set; }
-    public Account?       Acc     { get; set; }
+    public Subscription?       Sub     { get; set; }
+    public ClientConnection?   Client  { get; set; }
+    public Account?            Acc     { get; set; }
     public string         Subject { get; set; } = string.Empty;
     public string         Reply   { get; set; } = string.Empty;
     public byte[]?        Hdr     { get; set; }
@@ -195,10 +394,10 @@ internal sealed class InSysMsg
 internal sealed class InternalState
 {
     // ---- identity / sequencing ----
-    public Account?           Account    { get; set; }
-    public NatsClient?        Client     { get; set; }
-    public ulong              Seq        { get; set; }
-    public int                Sid        { get; set; }
+    public Account?            Account    { get; set; }
+    public ClientConnection?   Client     { get; set; }
+    public ulong               Seq        { get; set; }
+    public int                 Sid        { get; set; }
 
     // ---- remote server tracking ----
     /// <summary>Map of server ID → serverUpdate. Mirrors Go <c>servers map[string]*serverUpdate</c>.</summary>
@@ -216,7 +415,7 @@ internal sealed class InternalState
     /// Pending reply subject → handler map.
     /// Mirrors Go <c>replies map[string]msgHandler</c>.
     /// </summary>
-    public Dictionary<string, Action<Subscription, NatsClient, Account, string, string, byte[], byte[]>> Replies { get; set; } = new();
+    public Dictionary<string, Action<Subscription, ClientConnection, Account, string, string, byte[], byte[]>> Replies { get; set; } = new();
 
     // ---- queues ----
     /// <summary>Outbound message send queue. Mirrors Go <c>sendq *ipQueue[*pubMsg]</c>.</summary>
@@ -289,8 +488,8 @@ internal sealed class ServerUpdate
 /// </summary>
 internal sealed class PubMsg
 {
-    public NatsClient?  Client  { get; set; }
-    public string       Subject { get; set; } = string.Empty;
+    public ClientConnection?  Client  { get; set; }
+    public string             Subject { get; set; } = string.Empty;
     public string       Reply   { get; set; } = string.Empty;
     public ServerInfo?  Si      { get; set; }
     public byte[]?      Hdr     { get; set; }

dotnet/src/ZB.MOM.NatsNet.Server/NatsServerTypes.cs

@@ -88,6 +88,12 @@ public sealed class ServerInfo
     // LeafNode-specific
     [JsonPropertyName("leafnode_urls")]       public string[]? LeafNodeUrls     { get; set; }
 
+    // Events / heartbeat sequence number.
+    // Mirrors Go <c>Info.Seq uint64</c> used in server heartbeat messages.
+    [JsonPropertyName("seq")]
+    [System.Text.Json.Serialization.JsonIgnore(Condition = System.Text.Json.Serialization.JsonIgnoreCondition.WhenWritingDefault)]
+    public ulong Seq { get; set; }
+
     /// <summary>Returns a shallow clone of this <see cref="ServerInfo"/>.</summary>
     internal ServerInfo ShallowClone() => (ServerInfo)MemberwiseClone();
 }

reports/current.md

@@ -1,6 +1,6 @@
 # NATS .NET Porting Status Report
 
-Generated: 2026-03-01 12:56:43 UTC
+Generated: 2026-03-01 14:41:00 UTC
 
 ## Modules (12 total)
 
@@ -13,10 +13,10 @@ Generated: 2026-03-01 12:56:43 UTC
 | Status | Count |
 |--------|-------|
 | complete | 22 |
-| deferred | 363 |
+| deferred | 284 |
 | n_a | 24 |
 | stub | 1 |
-| verified | 3263 |
+| verified | 3342 |
 
 ## Unit Tests (3257 total)
 
@@ -35,4 +35,4 @@ Generated: 2026-03-01 12:56:43 UTC
 
 ## Overall Progress
 
-**5694/6942 items complete (82.0%)**
+**5773/6942 items complete (83.2%)**