diff --git a/libnetbox.lua b/libnetbox.lua
index 6c3c4a4..21fba25 100644
--- a/libnetbox.lua
+++ b/libnetbox.lua
@@ -1,29 +1,64 @@
 local component = require("component")
 local event = require("event")
+local serialization = require("serialization")
 require("util")
 require("libevent")
+require("checkarg")
+
+local function compress(t)
+    checktable(t)
+    return serialization.serialize(t)
+end
+
+local function decompress(x)
+    checkstring(x)
+    return serialization.unserialize(x)
+end
 
 local netbox_router_port = 9999
 local netbox_client_port = 9998
 
+local internal_port={}
+
 --- Auto Configure
 local modem=proxy("modem")
 local tunnel=proxy("tunnel")
 local is_router=false
 
--- APIs
+-- Hardware Check
 
-local internal_port={}
+local function doHardwareCheck()
+    if(modem==nil) then
+        error("Libnetbox[Warning]: modem not avaliable.")
+    end
+
+    if(tunnel==nil) then
+        is_router=false
+    else
+        is_router=true
+    end
+end
+
+-- APIs
 
 function SendData(target_address,port,...)
     if(not is_router) then
-        modem.broadcast(netbox_router_port,"NetBox","Direct",target_address,port,...)
+        local dt={}
+        dt["target"]=target_address
+        dt["method"]="Direct"
+        dt["data"]=compress(table.pack(...))
+
+        modem.broadcast(netbox_router_port,"NetBox",port,compress(dt))
     end
 end
 
 function BroadcastData(port,...)
     if(not is_router) then
-        modem.broadcast(netbox_router_port,"NetBox","Broadcast",port,...)
+        local dt={}
+        dt["method"]="Broadcast"
+        dt["data"]=compress(table.pack(...))
+
+        modem.broadcast(netbox_router_port,"NetBox",port,compress(dt))
     end
 end
 
@@ -65,20 +100,34 @@ function routerMain()
 
         if(e.receiverAddress==tunnel.address) then
             if(e.data[1]=="NetBoxAir") then
-                if(e.data[2]=="Direct") then
-                    modem.send(e.data[4],netbox_client_port,"NetBox",e.data[3],table.unpack(e.data,5))
-                elseif(e.data[2]=="Broadcast") then
-                    modem.broadcast(netbox_client_port,"NetBox",e.data[3],table.unpack(e.data,4))
+                local port=e.data[2]
+                local tt=decompress(e.data[3])
+
+                local dt={}
+                dt.senderAddress=tt.senderAddress
+                dt.data=tt.data
+
+                if(tt.method=="Direct") then
+                    modem.send(tt.target,netbox_client_port,"NetBox",port,compress(dt))
+                elseif(tt.method=="Broadcast") then
+                    modem.broadcast(netbox_client_port,"NetBox",port,compress(dt))
                 end
             end
         elseif(e.receiverAddress==modem.address) then
-            if(e.port==netbox_router_port) then
-                if(e.data[1]=="NetBox") then
-                    if(e.data[2]=="Direct") then
-                        tunnel.send("NetBoxAir","Direct",e.senderAddress,e.data[3],table.unpack(e.data,4))
-                    elseif(e.data[2]=="Broadcast") then
-                        tunnel.send("NetBoxAir","Broadcast",e.senderAddress,e.data[3],table.unpack(e.data,4))
-                    end
+            if(e.port==netbox_router_port and e.data[1]=="NetBox") then
+                local port=e.data[2]
+                local dt=decompress(e.data[3])
+
+                local tt={}
+                tt.data=dt.data
+                tt.method=dt.method
+                tt.senderAddress=e.senderAddress
+
+                if(dt.method=="Direct") then
+                    tt.target=dt.target
+                    tunnel.send("NetBoxAir",port,compress(tt))
+                elseif(dt.method=="Broadcast") then
+                    tunnel.send("NetBoxAir",port,compress(tt))
                 end
             end
         end
@@ -91,14 +140,36 @@ function routerMain()
     print("Router Stopped.")
 end
 
-function clientServiceStart(redirect)
+local _clientService_hand=-1
+
+function NetBoxInit(redirect)
     if(modem.open(netbox_client_port)==false) then
-        error("Failed to start client service. Real modem port can not be opened.")
+        if(modem.isOpen(netbox_client_port)==false) then
+            error("Failed to start client service. Real modem port can not be opened.")
+        else
+            print("libnetbox: Modem port has been opened. This may cause something wrong...")
+        end
     end
 
-    AddEventListener("modem_message",function(ev)
-        if(ev.data[1]=="NetBox" and internal_port[ev.data[3]]~=nil ) then
-            event.push("net_message",ev.receiverAddress,ev.data[2],ev.data[3],table.unpack(ev.data,4))
-        end
-    end)
+    if(_clientService_hand<0) then
+        _clientService_hand=AddEventListener("modem_message",function(ev)
+            if(ev.data[1]=="NetBox" and internal_port[ev.data[2]]~=nil) then
+                local dt=decompress(ev.data[3])
+                event.push("net_message",ev.receiverAddress,dt.senderAddress,ev.data[2],table.unpack(decompress(dt.data)))
+            end
+        end)
+    else
+        print("libnetbox: Service has been started before. This may cause something wrong...")
+    end
 end
+
+function NetBoxCleanUp()
+    if(_clientService_hand>=0) then
+         RemoveEventListener(_clientService_hand)
+         _clientService_hand=-1
+    end
+    modem.close(netbox_client_port)
+end
+
+-- Do hardware check
+doHardwareCheck()