diff --git a/apps/mirrorHost.lua b/apps/mirrorHost.lua
index 74c0536..ea5802a 100644
--- a/apps/mirrorHost.lua
+++ b/apps/mirrorHost.lua
@@ -16,7 +16,7 @@ mon.setBackgroundColor(colors.black)
 mon.clear()
 
 while true do
-  local socket = Socket.server(5901, true)
+  local socket = Socket.server(5901)
 
   print('mirror: connection from ' .. socket.dhost)
 
diff --git a/apps/telnet.lua b/apps/telnet.lua
index a1af509..39ef850 100644
--- a/apps/telnet.lua
+++ b/apps/telnet.lua
@@ -46,13 +46,14 @@ process:newThread('telnet_read', function()
       ct[v.f](unpack(v.args))
     end
   end
+  print('telnet_read exiting')
 end)
 
 ct.clear()
 ct.setCursorPos(1, 1)
 
 while true do
-  local e = { process:pullEvent() }
+  local e = { process:pullEvent(nil, true) }
   local event = e[1]
 
   if not socket.connected then
@@ -71,10 +72,11 @@ while true do
      event == 'mouse_click' or
      event == 'mouse_drag' then
 
-    socket:write({
-      type = 'shellRemote',
-      event = e,
-    })
+    if not socket:write({ type = 'shellRemote', event = e }) then
+      socket:close()
+      break
+    end
+
   elseif event == 'terminate' then
     socket:close()
     break
diff --git a/apps/trust.lua b/apps/trust.lua
index c04e7d3..f474724 100644
--- a/apps/trust.lua
+++ b/apps/trust.lua
@@ -53,7 +53,7 @@ local secretKey = os.getSecretKey()
 local publicKey = modexp(exchange.base, secretKey, exchange.primeMod)
 local password = SHA1.sha1(password)
 
-socket:write(Crypto.encrypt({ pk = publicKey }, password))
+socket:write(Crypto.encrypt({ pk = publicKey, dh = os.getComputerID() }, password))
 
 print(socket:read(2) or 'No response')
 
diff --git a/sys/apis/blocks.lua b/sys/apis/blocks.lua
index dbf3683..1f47309 100644
--- a/sys/apis/blocks.lua
+++ b/sys/apis/blocks.lua
@@ -298,6 +298,7 @@ function standardBlockDB:seedDB()
     [ '86:0' ] = 'pumpkin',
     [ '90:0' ] = 'air',
     [ '91:0' ] = 'pumpkin',
+    [ '92:0' ] = 'flatten', -- cake
     [ '93:0' ] = 'repeater',
     [ '94:0' ] = 'repeater',
     [ '96:0' ] = 'trapdoor',
diff --git a/sys/apis/socket.lua b/sys/apis/socket.lua
index 27fbfe9..6a9671e 100644
--- a/sys/apis/socket.lua
+++ b/sys/apis/socket.lua
@@ -31,41 +31,29 @@ function socketClass:read(timeout)
     return
   end
 
-  local timerId
-  local filter
-
-  if timeout then
-    timerId = os.startTimer(timeout)
-  elseif self.keepAlive then
-    timerId = os.startTimer(3)
-  else
-    filter = 'modem_message'
+  local data, distance = transport.read(self)
+  if data then
+    return data, distance
   end
 
-  while true do
-    local e, s, dport, dhost, msg, distance = os.pullEvent(filter)
-    if e == 'modem_message' and
-      dport == self.sport and dhost == self.shost and
-      msg then
+  local timerId = os.startTimer(timeout or 5)
 
-      if msg.type == 'DISC' then
-        -- received disconnect from other end
-        self.connected = false
-        self:close()
-        return
-      elseif msg.type == 'DATA' then
-        if msg.data then
-          if timerId then
-            os.cancelTimer(timerId)
-          end
-          return msg.data, distance
-        end
+  while true do
+    local e, id = os.pullEvent()
+
+    if e == 'transport_' .. self.dport then
+
+      data, distance = transport.read(self)
+      if data then
+        os.cancelTimer(timerId)
+        return data, distance
       end
-    elseif e == 'timer' and s == timerId then
+
+    elseif e == 'timer' and id == timerId then
       if timeout or not self.connected then
         break
       end
-      timerId = os.startTimer(3)
+      timerId = os.startTimer(5)
     end
   end
 end
@@ -75,8 +63,9 @@ function socketClass:write(data)
     Logger.log('socket', 'write: No connection')
     return false
   end
-  self.transmit(self.dport, self.dhost, {
+  transport.write(self, {
     type = 'DATA',
+    seq = self.wseq,
     data = data,
   })
   return true
@@ -91,45 +80,7 @@ function socketClass:close()
     self.connected = false
   end
   device.wireless_modem.close(self.sport)
-end
-
--- write a ping every second (too much traffic!)
-local function pinger(socket)
-
-  local process = require('process')
-
-  socket.keepAlive = true
-
-  Logger.log('socket', 'keepAlive enabled')
-
-  process:newThread('socket_ping', function()
-    local timerId = os.startTimer(1)
-    local timeStamp = os.clock()
-
-    while true do
-      local e, id, dport, dhost, msg = os.pullEvent()
-
-      if e == 'modem_message' then
-        if dport == socket.sport and
-          dhost == socket.shost and
-          msg and
-          msg.type == 'PING' then
-
-          timeStamp = os.clock()
-        end
-      elseif e == 'timer' and id == timerId then
-        if os.clock() - timeStamp > 3 then
-          Logger.log('socket', 'Connection timed out')
-          socket:close()
-          break
-        end
-        timerId = os.startTimer(1)
-        socket.transmit(socket.dport, socket.dhost, {
-          type = 'PING',
-        })
-      end
-    end
-  end)
+  transport.close(self)
 end
 
 local Socket = { }
@@ -139,12 +90,16 @@ local function loopback(port, sport, msg)
 end
 
 local function newSocket(isLoopback)
-  for i = 16384, 32768 do
+  for i = 16384, 32767 do
     if not device.wireless_modem.isOpen(i) then
       local socket = {
         shost = os.getComputerID(),
         sport = i,
         transmit = device.wireless_modem.transmit,
+        wseq = math.random(100, 100000),
+        rseq = math.random(100, 100000),
+        timers = { },
+        messages = { },
       }
       setmetatable(socket, { __index = socketClass })
 
@@ -169,7 +124,9 @@ function Socket.connect(host, port)
     type = 'OPEN',
     shost = socket.shost,
     dhost = socket.dhost,
-    t = Crypto.encrypt({ ts = os.time() }, exchange.publicKey),
+    t = Crypto.encrypt({ ts = os.time(), seq = socket.seq }, exchange.publicKey),
+    rseq = socket.wseq,
+    wseq = socket.rseq,
   })
 
   local timerId = os.startTimer(3)
@@ -185,11 +142,10 @@ function Socket.connect(host, port)
       Logger.log('socket', 'connection established to %d %d->%d',
                             host, socket.sport, socket.dport)
 
-      if msg.keepAlive then
-        pinger(socket)
-      end
       os.cancelTimer(timerId)
 
+      transport.open(socket)
+
       return socket
     end
   until e == 'timer' and id == timerId
@@ -199,7 +155,8 @@ end
 
 function trusted(msg, port)
 
-  if port == 19 then -- no auth for trust server
+  if port == 19 or msg.shost == os.getComputerID() then
+    -- no auth for trust server or loopback
     return true
   end
 
@@ -214,7 +171,7 @@ function trusted(msg, port)
   end
 end
 
-function Socket.server(port, keepAlive)
+function Socket.server(port)
 
   device.wireless_modem.open(port)
   Logger.log('socket', 'Waiting for connections on port ' .. port)
@@ -232,18 +189,16 @@ function Socket.server(port, keepAlive)
         socket.dport = dport
         socket.dhost = msg.shost
         socket.connected = true
-
+        socket.wseq = msg.wseq
+        socket.rseq = msg.rseq
         socket.transmit(socket.dport, socket.sport, {
           type = 'CONN',
           dhost = socket.dhost,
           shost = socket.shost,
-          keepAlive = keepAlive,
         })
         Logger.log('socket', 'Connection established %d->%d', socket.sport, socket.dport)
 
-        if keepAlive then
-          pinger(socket)
-        end
+        transport.open(socket)
         return socket
       end
     end
diff --git a/sys/apis/util.lua b/sys/apis/util.lua
index 46979aa..7ba934d 100644
--- a/sys/apis/util.lua
+++ b/sys/apis/util.lua
@@ -21,7 +21,7 @@ function Util.tryTimes(attempts, f, ...)
   return unpack(result)
 end
 
-function Util.print(pattern, ...)
+function Util.tostring(pattern, ...)
 
   local function serialize(tbl, width)
     local str = '{\n'
@@ -43,12 +43,15 @@ function Util.print(pattern, ...)
   end
 
   if type(pattern) == 'string' then
-    print(string.format(pattern, ...))
+    return string.format(pattern, ...)
   elseif type(pattern) == 'table' then
-    print(serialize(pattern, term.current().getSize()))
-  else
-    print(tostring(pattern))
+    return serialize(pattern, term.current().getSize())
   end
+  return tostring(pattern)
+end
+
+function Util.print(pattern, ...)
+  print(Util.tostring(pattern, ...))
 end
 
 function Util.runFunction(env, fn, ...)
diff --git a/sys/network/snmp.lua b/sys/network/snmp.lua
index 43b083c..ef9f74c 100644
--- a/sys/network/snmp.lua
+++ b/sys/network/snmp.lua
@@ -101,7 +101,7 @@ process:newThread('discovery_server', function()
   while true do
     local e, s, sport, id, info, distance = os.pullEvent('modem_message')
 
-    if sport == 999 then
+    if sport == 999 and tonumber(id) and type(info) == 'table' then
       if not network[id] then
         network[id] = { }
       end
diff --git a/sys/network/telnet.lua b/sys/network/telnet.lua
index a5fa35e..859bbf3 100644
--- a/sys/network/telnet.lua
+++ b/sys/network/telnet.lua
@@ -40,7 +40,7 @@ local function telnetHost(socket, termInfo)
     socket:close()
   end)
 
-  local queueThread = process:newThread('telnet_read', function()
+  process:newThread('telnet_read', function()
     while true do
       local data = socket:read()
       if not data then
@@ -49,7 +49,6 @@ local function telnetHost(socket, termInfo)
 
       if data.type == 'shellRemote' then
         local event = table.remove(data.event, 1)
-
         shellThread:resume(event, unpack(data.event))
       end
     end
@@ -65,7 +64,10 @@ local function telnetHost(socket, termInfo)
       break
     end
     if socket.queue then
-      socket:write(socket.queue)
+      if not socket:write(socket.queue) then
+        print('telnet: connection lost to ' .. socket.dhost)
+        break
+      end
       socket.queue = nil
     end
   end
diff --git a/sys/network/trust.lua b/sys/network/trust.lua
index 282b56f..6a981da 100644
--- a/sys/network/trust.lua
+++ b/sys/network/trust.lua
@@ -17,9 +17,9 @@ process:newThread('trust_server', function()
         socket:write('No password has been set')
       else
         data = Crypto.decrypt(data, password)
-        if data and data.pk then
+        if data and data.pk and data.dh then
           local trustList = Util.readTable('.known_hosts') or { }
-          trustList[socket.dhost] = data.pk
+          trustList[data.dh] = data.pk
           Util.writeTable('.known_hosts', trustList)
 
           socket:write('Trust accepted')
diff --git a/sys/services/transort.lua b/sys/services/transort.lua
new file mode 100644
index 0000000..53bff02
--- /dev/null
+++ b/sys/services/transort.lua
@@ -0,0 +1,97 @@
+--[[
+  Low level socket protocol implementation.
+
+  * sequencing
+  * write acknowledgements
+  * background read buffering
+]]--
+
+multishell.setTitle(multishell.getCurrent(), 'Net transport')
+
+local computerId = os.getComputerID()
+
+_G.transport = {
+  timers  = { },
+  sockets = { },
+}
+
+function transport.open(socket)
+  transport.sockets[socket.sport] = socket
+end
+
+function transport.read(socket)
+  local data = table.remove(socket.messages, 1)
+  if data then
+    return unpack(data)
+  end
+end
+
+function transport.write(socket, data)
+
+  --debug('>> ' .. Util.tostring({ type = 'DATA', seq = socket.wseq }))
+  socket.transmit(socket.dport, socket.dhost, data)
+
+  local timerId = os.startTimer(2)
+
+  transport.timers[timerId] = socket
+  socket.timers[socket.wseq] = timerId
+
+  socket.wseq = socket.wseq + 1
+end
+
+function transport.close(socket)
+  transport.sockets[socket.sport] = nil
+end
+
+print('Net transport started')
+
+while true do
+  local e, timerId, dport, dhost, msg, distance = os.pullEvent()
+
+  if e == 'timer' then
+    local socket = transport.timers[timerId]
+    if socket and socket.connected then
+      socket:close()
+      transport.timers[timerId] = nil
+    end
+
+  elseif e == 'modem_message' and dhost == computerId and msg then
+    local socket = transport.sockets[dport]
+    if socket and socket.connected then
+
+      --if msg.type then debug('<< ' .. Util.tostring(msg)) end
+
+      if msg.type == 'DISC' then
+        -- received disconnect from other end
+        socket.connected = false
+        socket:close()
+
+      elseif msg.type == 'ACK' then
+        local timerId = socket.timers[msg.seq]
+
+        os.cancelTimer(timerId)
+        socket.timers[msg.seq] = nil
+        transport.timers[timerId] = nil
+
+      elseif msg.type == 'DATA' and msg.data then
+        if msg.seq ~= socket.rseq then
+          socket:close()
+        else
+          socket.rseq = socket.rseq + 1
+          table.insert(socket.messages, { msg.data, distance })
+
+          -- use resume instead ??
+          if not socket.messages[2] then  -- table size is 1
+            os.queueEvent('transport_' .. dport)
+          end
+
+          --debug('>> ' .. Util.tostring({ type = 'ACK', seq = msg.seq }))
+          socket.transmit(socket.dport, socket.dhost, {
+            type = 'ACK',
+            seq = msg.seq,
+          })
+        end
+      end
+    end
+  end
+end