diff --git a/OOequipment/Equipment.m b/OOequipment/Equipment.m
index 6c4de88..821b90e 100644
--- a/OOequipment/Equipment.m
+++ b/OOequipment/Equipment.m
@@ -6,12 +6,14 @@ classdef Equipment < handle
         name
         tcp
         channel
+        %lock
     end
     
     methods
         function ecq = Equipment(name,ipAddress,port,channel)
             ecq.name = name;
             ecq.tcp = Equipment.getTCP(ipAddress,port);
+            
             ecq.channel = channel;
         end
         function idn(ecq)
@@ -20,26 +22,39 @@ classdef Equipment < handle
             fprintf(ecq.tcp,'++read');
             fprintf(fscanf(ecq.tcp));
         end
-        function starttcp(DMM)
-            fopen(DMM.tcp);
+        function delete(ecq)
+            %zorgen dat het device geunlocked is!
+            
+            Equipment.getTCP(ecq.tcp.RemoteHost,-1);
         end
     end
     methods (Static)
         function tcpobject = getTCP(ipAddress,port)
             persistent tcpconnection;
             ipname = Equipment.ip2structname(ipAddress);
-            if isempty(tcpconnection)
-                tcpconnection = struct;
-            end
-            
-            if ~isfield(tcpconnection, ipname)
-                tcpconnection.(ipname).tcp = tcpip(ipAddress,port);
-                tcpconnection.(ipname).nopen = 1;
-                fopen(tcpconnection.(ipname).tcp);
+            if port > 0
+                if isempty(tcpconnection)
+                    tcpconnection = struct;
+                end
+
+                if ~isfield(tcpconnection, ipname)
+                    tcpconnection.(ipname).tcp = tcpip(ipAddress,port);
+                    tcpconnection.(ipname).nopen = 1;
+                    fopen(tcpconnection.(ipname).tcp);
+                else
+                    tcpconnection.(ipname).nopen = tcpconnection.(ipname).nopen + 1;
+                end
+                tcpobject = tcpconnection.(ipname).tcp;
+            elseif port == -1
+                if tcpconnection.(ipname).nopen > 1
+                    tcpconnection.(ipname).nopen = tcpconnection.(ipname).nopen - 1;
+                else
+                    fclose(tcpconnection.(ipname).tcp);
+                    tcpconnection = rmfield(tcpconnection,ipname);
+                end
             else
-                tcpconnection.(ipname).nopen = tcpconnection.(ipname).nopen + 1;
+                error([num2str(port),' is not a valid port number try a value between 1 and 65535.']);
             end
-            tcpobject = tcpconnection.(ipname).tcp;
         end
         
         function iptest(ipAddress)