diff --git a/Makefile b/Makefile
index 54aaebf..8b95ef4 100644
--- a/Makefile
+++ b/Makefile
@@ -6,7 +6,7 @@ CXXFLAGS:= -std=gnu++17 -Wall -O3 -MMD -MP -ggdb -fno-omit-frame-pointer -Iext/C
 
 # CXXFLAGS += -Wno-delete-non-virtual-dtor
 
-PROGRAMS = navparse ubxtool navnexus navrecv navdump testrunner navdisplay tlecatch
+PROGRAMS = navparse ubxtool navnexus navcat navrecv navdump testrunner navdisplay tlecatch
 
 all: navmon.pb.cc $(PROGRAMS)
 
@@ -33,6 +33,10 @@ navdisplay: navdisplay.o ext/fmt-5.2.1/src/format.o bits.o navmon.pb.o gps.o eph
 navnexus: navnexus.o ext/fmt-5.2.1/src/format.o  $(SIMPLESOCKETS) ubx.o bits.o navmon.pb.o storage.o
 	$(CXX) -std=gnu++17 $^ -o $@ -L/usr/local/lib -pthread -lprotobuf
 
+navcat: navcat.o ext/fmt-5.2.1/src/format.o  $(SIMPLESOCKETS) ubx.o bits.o navmon.pb.o storage.o navmon.o
+	$(CXX) -std=gnu++17 $^ -o $@ -L/usr/local/lib -pthread -lprotobuf
+
+
 navrecv: navrecv.o ext/fmt-5.2.1/src/format.o $(SIMPLESOCKETS) navmon.pb.o storage.o
 	$(CXX) -std=gnu++17 $^ -o $@ -L/usr/local/lib -pthread -lprotobuf  
 
diff --git a/navcat.cc b/navcat.cc
new file mode 100644
index 0000000..d431f6f
--- /dev/null
+++ b/navcat.cc
@@ -0,0 +1,172 @@
+#include "comboaddress.hh"
+#include "sclasses.hh"
+#include <thread>
+#include <signal.h>
+#include "navmon.pb.h"
+#include "fmt/format.h"
+#include "fmt/printf.h"
+#include <mutex>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdexcept>
+#include <sys/types.h>
+#include "storage.hh"
+#include <dirent.h>
+#include <inttypes.h>
+#include "navmon.hh"
+
+using namespace std;
+
+void unixDie(const std::string& str)
+{
+  throw std::runtime_error(str+string(": ")+string(strerror(errno)));
+}
+
+time_t parseTime(std::string_view in)
+{
+  time_t now=time(0);
+
+  vector<string> formats({"%Y-%m-%d %H:%M", "%Y%m%d %H%M", "%H:%M", "%H%M"});
+  for(const auto& f : formats) {
+    struct tm tm;
+    memset(&tm, 0, sizeof(tm));
+
+    localtime_r(&now, &tm);
+    tm.tm_isdst = -1;
+    tm.tm_sec = 0;
+    char* res = strptime(&in[0], f.c_str(), &tm);
+    if(res && !*res) {
+      cerr<<"Matched on "<<f<<endl;
+      return mktime(&tm);
+    }
+  }
+  
+  throw runtime_error("Can only parse %Y-%m-%d %H:%M");
+}
+
+
+vector<uint64_t> getSources(string_view dirname)
+{
+  DIR *dir = opendir(&dirname[0]);
+  if(!dir)
+    unixDie("Listing metrics from statistics storage "+(string)dirname);
+  struct dirent *result=0;
+  vector<uint64_t> ret;
+  for(;;) {
+    errno=0;
+    if(!(result = readdir(dir))) {
+      closedir(dir);
+      if(errno)
+        unixDie("Reading directory entry "+(string)dirname);
+      else
+        break;
+    }
+    if(result->d_name[0] != '.') {
+      uint64_t src;
+      if(sscanf(result->d_name, "%08" PRIx64, &src)==1)
+        ret.push_back(src);
+    }
+  }
+
+  sort(ret.begin(), ret.end());
+  return ret;
+}
+
+static size_t writen2(int fd, const void *buf, size_t count)
+{
+  const char *ptr = (char*)buf;
+  const char *eptr = ptr + count;
+
+  ssize_t res;
+  while(ptr != eptr) {
+    res = ::write(fd, ptr, eptr - ptr);
+    if(res < 0) {
+      throw runtime_error("failed in writen2: "+string(strerror(errno)));
+    }
+    else if (res == 0)
+      throw EofException();
+
+    ptr += (size_t) res;
+  }
+
+  return count;
+}
+
+
+
+void sendProtobuf(string_view dir, time_t startTime, time_t stopTime=0)
+{
+  pair<uint64_t, uint64_t> start = {startTime, 0};
+
+  // so we have a ton of files, and internally these are not ordered
+  map<string,uint32_t> fpos;
+  vector<NavMonMessage> nmms;
+  for(;;) {
+    auto srcs = getSources(dir);
+    nmms.clear();
+    for(const auto& src: srcs) {
+      string fname = getPath(dir, start.first, src);
+      int fd = open(fname.c_str(), O_RDONLY);
+      if(fd < 0)
+        continue;
+      uint32_t offset= fpos[fname];
+      if(lseek(fd, offset, SEEK_SET) < 0) {
+        cerr<<"Error seeking: "<<strerror(errno) <<endl;
+        close(fd);
+        continue;
+      }
+      cerr <<"Seeked to position "<<fpos[fname]<<" of "<<fname<<endl;
+      NavMonMessage nmm;
+
+      uint32_t looked=0;
+      while(getNMM(fd, nmm, offset)) {
+        // don't drop data that is only 5 seconds too old
+        if(make_pair(nmm.localutcseconds() + 5, nmm.localutcnanoseconds()) >= start) {
+          nmms.push_back(nmm);
+        }
+        ++looked;
+      }
+      cerr<<"Harvested "<<nmms.size()<<" events out of "<<looked<<endl;
+      fpos[fname]=offset;
+      close(fd);
+    }
+    sort(nmms.begin(), nmms.end(), [](const auto& a, const auto& b)
+         {
+           return make_pair(a.localutcseconds(), b.localutcnanoseconds()) <
+             make_pair(b.localutcseconds(), b.localutcnanoseconds());
+         });
+
+    for(const auto& nmm: nmms) {
+      std::string out;
+      nmm.SerializeToString(&out);
+      std::string buf="bert";
+      uint16_t len = htons(out.size());
+      buf.append((char*)(&len), 2);
+      buf+=out;
+      writen2(1, buf.c_str(), buf.size());
+    }
+    if(3600 + start.first - (start.first%3600) < stopTime)
+      start.first = 3600 + start.first - (start.first%3600);
+    else {
+      break;
+    }
+  }
+}
+
+
+int main(int argc, char** argv)
+{
+  signal(SIGPIPE, SIG_IGN);
+  if(argc < 3) {
+    cout<<"Syntax: navcat storage start stop"<<endl;
+    return(EXIT_FAILURE);
+  }
+  time_t startTime = parseTime(argv[2]);
+  time_t stopTime = parseTime(argv[3]);
+
+  cerr<<"Emitting from "<<humanTime(startTime) << " to " << humanTime(stopTime) << endl;
+  sendProtobuf(argv[1], startTime, stopTime);
+  
+}