Changed assignment attempt usage to object test. Used /examples/net/same_mach as guide.

Author:halw
Date:2012-04-07T15:46:24.000000Z


git-svn-id: https://svn.eiffel.com/eiffel-org/trunk@1069 abb3cda0-5349-4a8f-a601-0c33ac3a8c38

documentation/current/solutions/networking/eiffelnet/eiffelnet-tutorial/obtaining-finer-degree-control.wiki

@@ -44,11 +44,17 @@ Whenever the server needs to exchange objects with one of the clients, it obtain
 
 Procedure <eiffel>accept</eiffel> ensures synchronization with the client. When communication is established, <eiffel>accept</eiffel> creates a new socket which will be accessible through attribute <eiffel>accepted</eiffel>, whose value is here assigned to the local entity <eiffel>soc2</eiffel>. To receive objects, the server will use operations of the form introduced earlier ( [[An overview of EiffelNet Mechanisms|An overview of EiffelNet, sending and receiving object structures]] ): 
 <code>
-            struct ?= soc2.retrieved</code>
+            if attached {SOME_EXPECTED_TYPE} soc2.retrieved as l_temp then
+--             soc2.retrieved was attached to an object of the expected type. Now that object is attached to `l_temp'
+--             Proceed with normal computation, typically involving calls of the form l_temp.some_feature
+            else
+--             soc2.retrieved was not attached to an object of the expected type.
+            end
+</code>
 
 applying to <eiffel>soc2</eiffel>, not <eiffel>soc1</eiffel>; this makes <eiffel>soc1</eiffel> available to accept connections with other clients, a fundamental feature of client-server mechanisms. 
 
-The operation <eiffel>soc2</eiffel>. <eiffel>close</eiffel> which terminates the above sequence closes the new socket. In principle this is not necessary, since garbage collection should eventually reclaim the socket object, and the <eiffel>dispose</eiffel> procedure of the corresponding socket class includes a call to <eiffel>close</eiffel>. But the risk exists that you run out of sockets before garbage collection reclaims all currently opened sockets, so it is preferable to include the <eiffel>close</eiffel> calls explicitly. 
+The operation <eiffel>soc2.close</eiffel> which terminates the above sequence closes the new socket. In principle this is not necessary, since garbage collection should eventually reclaim the socket object, and the <eiffel>dispose</eiffel> procedure of the corresponding socket class includes a call to <eiffel>close</eiffel>. But the risk exists that you run out of sockets before garbage collection reclaims all currently opened sockets, so it is preferable to include the <eiffel>close</eiffel> calls explicitly. 
 
 At the end of the processing it is necessary to close the original socket <eiffel>soc1</eiffel> but also to unlink it. The feature <eiffel>cleanup</eiffel> from class <eiffel>SOCKET</eiffel> takes care of both closing and unlinking. 
 
@@ -67,12 +73,11 @@ creation
 	
 feature
 	
-    soc1, soc2: UNIX_STREAM_SOCKET
-	
     make
             -- Accept communication with client and exchange messages
         local 
             count: INTEGER
+            soc1: detachable UNIX_STREAM_SOCKET
         do 
             create soc1.make_server ("/tmp/here") 
             from 
@@ -81,35 +86,37 @@ feature
             until 
                 count = 3
             loop 
-                process -- See below
+                process (soc1) -- See below
                 count := count + 1
             end 
             soc1.cleanup
         rescue 
+            if soc1 /= Void then
                 soc1.cleanup
             end
+        end
 	
-    process
+    process (soc1: UNIX_STREAM_SOCKET)
             -- Receive a message, extend it, and send it back
-        local 
-            our_new_list: OUR_MESSAGE
         do
             soc1.accept
-            soc2 ?= soc1.accepted
+            if attached soc1.accepted as l_soc2 then
-            our_new_list ?= retrieved (soc2) 
+                if attached {OUR_MESSAGE} retrieved (l_soc2) as l_our_new_list then 
                     from 
-                our_new_list.start
+                        l_our_new_list.start
                     until 
-                our_new_list.after
+                        l_our_new_list.after
                     loop 
-                io.putstring (our_new_list.item) 
+                        io.putstring (l_our_new_list.item) 
                         io.new_line
-                our_new_list.forth
+                        l_our_new_list.forth
+                    end 
+                    l_our_new_list.extend ("%N I'm back.%N") 
+                    l_our_new_list.independent_store (l_soc2) 
                 end
-            our_new_list.extend ("%N I'm back.%N") 
-            our_new_list.independent_store (soc2) 
                 soc2.close
             end
+        end
 	
 end
 </code>
@@ -129,40 +136,45 @@ creation
 	
 feature
 	
-    soc1: UNIX_STREAM_SOCKET
-	
     make
             -- Establish communication with server, and exchange messages
+        local
+            soc1: detachable UNIX_STREAM_SOCKET
         do 
             create soc1.make_client ("/tmp/here") 
             soc1.connect
-            process -- See below
+            process (soc1) -- See below
             soc1.cleanup
         rescue 
+            if soc1 /= Void then
                 soc1.cleanup
             end
+        end
 	
-    process
+    process (soc1: UNIX_STREAM_SOCKET)
             -- Build a message to server, receive answer, build
             -- modified message from that answer, and print it.
         local 
-            our_list, our_new_list: OUR_MESSAGE
+            our_list: OUR_MESSAGE
         do 
             create our_list.make
-            our_list.extend("This"); our_list.extend (" is") 
+            our_list.extend("This")
-            our_list.extend (" our"); our_list.extend (" test") 
+            our_list.extend (" is") 
+            our_list.extend (" our")
+            our_list.extend (" test") 
             our_list.independent_store (soc1) 
-            our_new_list ?= soc1.retrieved
+            if attached {OUR_MESSAGE} our_list.retrieved (soc1) as l_our_new_list then
                 from 
-                our_new_list.start
+                    l_our_new_list.start
                 until 
-                our_new_list.after
+                    l_our_new_list.after
                 loop 
-                io.putstring (our_new_list.item) 
+                    io.putstring (l_our_new_list.item) 
-                our_new_list.forth
+                    l_our_new_list.forth
                 end 
                 io.new_line
             end
+        end
 	
 end
 </code>