diff --git a/ouroboros-network-framework/src/Ouroboros/Network/ConnectionManager/Core.hs b/ouroboros-network-framework/src/Ouroboros/Network/ConnectionManager/Core.hs
index 49e5f545610..16e4c76de4a 100644
--- a/ouroboros-network-framework/src/Ouroboros/Network/ConnectionManager/Core.hs
+++ b/ouroboros-network-framework/src/Ouroboros/Network/ConnectionManager/Core.hs
@@ -114,13 +114,23 @@ withConnectionManager ConnectionManagerArguments {
             ConnectionHandler (WithResponderMode inboundHandler) ->
               ConnectionManager
                 (WithResponderMode
-                  (includeConnection stateVar mainThreadId inboundHandler Inbound))
+                  InboundConnectionManager {
+                      icmIncludeConnection =
+                        includeConnection stateVar mainThreadId inboundHandler Inbound,
+                      icmNumberOfConnections =
+                        countConnections stateVar
+                    })
 
             ConnectionHandler (WithInitiatorResponderMode outboundHandler inboundHandler) ->
               ConnectionManager
                 (WithInitiatorResponderMode
                   (connectAndInclude stateVar mainThreadId outboundHandler)
-                  (includeConnection stateVar mainThreadId inboundHandler Inbound))
+                  InboundConnectionManager {
+                      icmIncludeConnection =
+                        includeConnection stateVar mainThreadId inboundHandler Inbound,
+                      icmNumberOfConnections =
+                        countConnections stateVar
+                    })
 
     k connectionManager
       `finally` do
@@ -132,6 +142,9 @@ withConnectionManager ConnectionManagerArguments {
               >> close connectionSnocket chSocket )
           state
   where
+    countConnections :: StrictTMVar m (State peerAddr socket muxPromise m) -> STM m Int
+    countConnections stateVar = Map.size <$> readTMVar stateVar
+
     -- Include a connection in the 'State'; we use this for both inbound and
     -- outbound (via 'connectAndInclude' below) connections.
     --
diff --git a/ouroboros-network-framework/src/Ouroboros/Network/ConnectionManager/Types.hs b/ouroboros-network-framework/src/Ouroboros/Network/ConnectionManager/Types.hs
index 9e62b6f187e..6d62c4c2095 100644
--- a/ouroboros-network-framework/src/Ouroboros/Network/ConnectionManager/Types.hs
+++ b/ouroboros-network-framework/src/Ouroboros/Network/ConnectionManager/Types.hs
@@ -19,10 +19,12 @@ module Ouroboros.Network.ConnectionManager.Types
   , ConnectionManagerArguments (..)
     -- * 'ConnectionManager'
   , ConnectionManager (..)
+  , InboundConnectionManager (..)
   , IncludeOutboundConnection
   , includeOutboundConnection
   , IncludeInboundConnection
   , includeInboundConnection
+  , numberOfConnections
     -- * Exceptions
   , ExceptionInHandler (..)
     -- * Mux types
@@ -188,6 +190,19 @@ type IncludeInboundConnection  socket peerAddr muxPromise m
     = socket -> peerAddr -> m (STM m muxPromise)
 
 
+-- | Inbound connection manager.  For a server implementation we also need to
+-- know how many connections are now managed by the connection manager.
+--
+-- This type is an internal detail of 'Ouroboros.Network.ConnectionManager'
+--
+data InboundConnectionManager (muxMode :: MuxMode) socket peerAddr muxPromise m where
+    InboundConnectionManager
+      :: HasResponder muxMode ~ True
+      => { icmIncludeConnection   :: IncludeInboundConnection socket peerAddr muxPromise m
+         , icmNumberOfConnections :: STM m Int
+         }
+      -> InboundConnectionManager muxMode socket peerAddr muxPromise m
+
 -- | 'ConnectionManager'.
 --
 -- We identify resources (e.g. 'Network.Socket.Socket') by their address.   It
@@ -198,10 +213,14 @@ type IncludeInboundConnection  socket peerAddr muxPromise m
 --
 newtype ConnectionManager (muxMode :: MuxMode) socket peerAddr muxPromise m = ConnectionManager {
     runConnectionManager
-      :: WithMuxMode muxMode (IncludeOutboundConnection        peerAddr muxPromise m)
-                             (IncludeInboundConnection  socket peerAddr muxPromise m)
+      :: WithMuxMode muxMode (IncludeOutboundConnection                 peerAddr muxPromise m)
+                             (InboundConnectionManager  muxMode socket peerAddr muxPromise m)
   }
 
+--
+-- ConnectionManager API
+--
+
 -- | Include outbound connection into 'ConnectionManager'.
 --
 includeOutboundConnection :: HasInitiator muxMode ~ True
@@ -212,10 +231,21 @@ includeOutboundConnection = withInitiatorMode . runConnectionManager
 -- | Include an inbound connection into 'ConnectionManager'.
 --
 includeInboundConnection :: HasResponder muxMode ~ True
-                          => ConnectionManager muxMode socket peerAddr muxPromise m
-                          -> IncludeInboundConnection  socket peerAddr muxPromise m
-includeInboundConnection = withResponderMode . runConnectionManager
+                         => ConnectionManager muxMode socket peerAddr muxPromise m
+                         -> IncludeInboundConnection  socket peerAddr muxPromise m
+includeInboundConnection =  icmIncludeConnection . withResponderMode . runConnectionManager
 
+-- | Number of currently included connections.
+--
+-- Note: we count all connection: both inbound and outbound.  In a future
+-- version we could count only inbound connections, but this will require
+-- tracking state inside mux if the responder side has started running (through
+-- on-demand interface).  This is currently not exposed by mux.
+--
+numberOfConnections :: HasResponder muxMode ~ True
+                    => ConnectionManager muxMode socket peerAddr muxPromise m
+                    -> STM m Int
+numberOfConnections = icmNumberOfConnections . withResponderMode . runConnectionManager
 
 --
 -- Tracing