diff --git a/navrecv.cc b/navrecv.cc
index 01d7da1..01672e3 100644
--- a/navrecv.cc
+++ b/navrecv.cc
@@ -16,6 +16,7 @@
 #include "version.hh"
 #include <netinet/tcp.h>
 #include "navmon.hh"
+#include <mutex>
 
 static char program[]="navrecv";
 
@@ -140,8 +141,94 @@ void writeToDisk(time_t s, uint64_t sourceid, std::string_view message)
   }
 }
 
+// This is used to report clients, so we can log them
+// The idea is that cleanup runs from the Sentinel which, when destroyed, will remove the entry
+struct ClientKeeper
+{
+  struct ClientStatus
+  {
+    bool oldProtocol;
+    time_t lastMessage;
+    int station;
+    uint64_t messages{0};
+  };
+
+  struct Sentinel
+  {
+    Sentinel(ClientKeeper* parent, const ComboAddress& us) : d_parent(parent), d_us(us)
+    {
+    }
+
+    Sentinel(Sentinel&& s)
+    {
+      //      cerr<<"Moved!"<<endl;
+      d_parent = s.d_parent;
+      d_us = s.d_us;
+      s.d_parent=0;
+    }
+    
+    ~Sentinel()
+    {
+      //      cerr<<"Destructor"<<endl;
+      if(d_parent) {
+	d_parent->remove(d_us);
+      }
+      else
+	; //cerr<<"   but we were moved already!\n";
+
+    }
+    void update(int station, bool oldProtocol)
+    {
+      time_t now = time(0);
+      std::lock_guard<std::mutex> l(d_parent->d_mut);
+      ClientStatus& cs = d_parent->d_clients[d_us];
+      cs.station = station;
+      cs.lastMessage = now;
+      cs.messages++;
+      cs.oldProtocol = oldProtocol;
+    }
+    ClientKeeper* d_parent;
+    ComboAddress d_us;
+  };
+
+  Sentinel reportClient(const ComboAddress& client)
+  {
+    Sentinel s2(this, client);
+    
+    std::lock_guard<std::mutex> l(d_mut);
+    d_clients[client];
+    return s2;
+  }
+
+  void remove(const ComboAddress& client)
+  {
+    std::lock_guard<std::mutex> l(d_mut);
+    d_clients.erase(client);
+  }
+
+  void dump()
+  {
+    std::lock_guard<std::mutex> l(d_mut);
+    string format("{:<50}{:<5}{:<10}{:<10}{:<10}\n");
+    ofstream out("clients.bak");
+    time_t now=time(0);
+    out<< fmt::format(format, "IP Address", "ID", "Protocol", "Messages", "Age");
+    for(const auto& c : d_clients) {
+      out << fmt::format(format, c.first.toStringWithPort(), c.second.station, c.second.oldProtocol ? "Old" : "New", c.second.messages, now-c.second.lastMessage);
+    }
+    out.close();
+    unlink("clients.txt");
+    rename("clients.bak", "clients.txt");
+  }
+  
+  map<ComboAddress, ClientStatus> d_clients;
+  std::mutex d_mut;
+};
+
+ClientKeeper g_ckeeper;
+
 // note that this moves the socket
-void recvSession2(Socket&& uns, ComboAddress client)
+void recvSession2(Socket&& uns, ComboAddress client, ClientKeeper::Sentinel& sentinel)
 {
   string secret = SRead(uns, 8); // ignored for now
   cerr << "Entering compressed session for "<<client.toStringWithPort()<<endl;
@@ -177,6 +264,7 @@ void recvSession2(Socket&& uns, ComboAddress client)
     memcpy(&denum, num.c_str(), 4);
     denum = htonl(denum);
     //    cerr<<"Received message "<<denum<< " "<<nmm.localutcseconds()<<" " << nmm.localutcnanoseconds()/1000000000.0<<endl;
+    sentinel.update(nmm.sourceid(), false);
     writeToDisk(nmm.localutcseconds(), nmm.sourceid(), out);
 
     if(first) {
@@ -201,6 +289,9 @@ void recvSession(int s, ComboAddress client)
     SSetsockopt(s, SOL_SOCKET, SO_KEEPALIVE, 1); // saves file descriptors
     cerr<<"Receiving messages from "<<client.toStringWithPort()<<endl;
     bool first=true;
+
+    ClientKeeper::Sentinel sentinel=g_ckeeper.reportClient(client);
+    
     for(int count=0;;++count) {
       string part=SRead(sock, 4);
       if(part.empty()) {
@@ -209,7 +300,7 @@ void recvSession(int s, ComboAddress client)
       }
       if(part != "bert") {
         if(part == "RNIE")
-          return recvSession2(std::move(sock), client);  // protocol v2, socket is moved cuz cleanup is special
+          return recvSession2(std::move(sock), client, sentinel);  // protocol v2, socket is moved cuz cleanup is special
         cerr << "Message "<<count<<", wrong magic from "<<client.toStringWithPort()<<": "<<makeHexDump(part)<<endl;
         break;
       }
@@ -235,6 +326,7 @@ void recvSession(int s, ComboAddress client)
         cerr<<"\tstation: "<<nmm.sourceid() << endl;
         first=false;
       }
+      sentinel.update(nmm.sourceid(), true);
       writeToDisk(nmm.localutcseconds(), nmm.sourceid(), out);
     }
   }
@@ -286,8 +378,10 @@ int main(int argc, char** argv)
 
   thread recvThread(recvListener, std::move(receiver), recvaddr);
   recvThread.detach();
- 
+
+  sleep(5);
   for(;;) {
-    sleep(1);
+    g_ckeeper.dump();
+    sleep(10);
   }
 }