DS LABS DISTRIBUTED SYSTEMS PRACTICAL EXERCISES

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1 DS LABS DISTRIBUTED SYSTEMS PRACTICAL EXERCISES Java Streams and TCP Sckets Jsé María F Mrán, 2013 Creative Cmmns License 9 OCTUBRE

2 JAVA SOCKETS (TCP) 7 web server 7 firefx Applicatins Applicatins ( , 80, , 1200) Mux/Demux key fr TCP Java Sckets are an abstractin f a TCP reliable channel Sckets ffer a namespace fr ses and TCP channels 5 80 Sessin (Sckets) Sessin (Sckets) A way t identify a s running n a cmputer in internet Scket knwledge is essential fr learning RMI (Distributed Objects) TCP TCP IP 3 IP internet 9 OCTUBRE

3 JAVA SOCKETS (TCP) Sckets represent a TCP cnnectin but they hide the details regarding the s f cnnectin establishment and teardwn Cnnectin requested SERVER (Stream Scket) SYN SYN and ACK CLIENT (Stream Scket) Cnnectin indicatin TCP tcl is virtuallly hidden Except fr activatin/deactivatin f certain features: ACK + Data Cnnectin acknwledged Nagel s algrithm Cnnectin established A simple intrductin t the Client/Server distributed cmputing mdel (C/S) Time 9 OCTUBRE

4 JAVA SOCKET CLIENT/SERVER Server creates a ServerScket n a well knwn prt (80, fr example) SERVER CLIENT This is the Welcme Scket Welcme Scket Listens frever fr cnnectin requests frm Clients If ne arrives, executes 3-way handshake and creates a delegate scket t care fr the frthcming i/ peratins Client creates a Scket and cnnects it t server s IP/PORT Welcme Scket Delegate Scket º: Three-way handshake 2º: Full-duplex channel established 1200 Client scket This Scket is adequate fr perfrming i/ peratins 9 OCTUBRE

5 JAVA SOCKETS, EXAMPLES SERVER creates a ServerScket and binds it t a well knwn prt CLIENT creates a Scket and cnnects it t server s ip/prt SERVER CLIENT SERVER waits fr new cnnectin request Welcme Scket 80 1º: Three-way handshake 1200 Client scket 2º: Full-duplex channel established Delegate Scket 80 9 OCTUBRE

6 JAVA STREAMS, ABSTRACT CLASSES Streams, an abstractin: Ordered sequence f bytes Strage and retrieval are dne sequentially Adequate fr almst any external device Abstract classes InputStream Methds fr reading data and stream navigatin OS must allcate resur beynd memry IOExceptin, checked exceptin (try/catch) OutputStream Methds fr writing data flush(): utput streams usually allcate a buffer t stre the data being written 9 OCTUBRE

7 JAVA STREAMS LAYERING Streams can be wrapped in ther streams t vide incremental functinality Decratr/Wrapper patterns Primitive: Talk t external devi (underlying streams) FileInputStream / FileOutputStream ObjectInputStream / ObjectOutputStream Intermediate streams: Wrap arund already existing streams If yu clse a stream that enclses a scket, clse() and flush() pagate t sckets DataInputStream / DataOutputStream (Binary, byte streams) Readers / Writers (Unicde characters and strings) Other pssibilities: Classes fr buffered streams Cmpressed streams Others 9 OCTUBRE

8 JAVA STREAMS LAYERING The OutputStream f Scket s gets wrapped int an ObjectOutputStream instance whse name is s Nw, we use s t transmit data much mre easily than with s 9 OCTUBRE

9 OBJECT OUTPUT STREAM Java ObjectInputStream() and ObjectOutputStream() classes serve fr transmitting Java bjects directly in a seamlessly manner ver these streams When Java transmits an bject it send a series f rdered bytes ver a stream, that rdered sequence, upn receptin is deserialized and trnasfrmed int a cpy f the riginal bject in the addressing space f the receiving JVM Object serializatin example: 9 OCTUBRE

10 TWO-SESSION LABORATORY EXERCISE Design and build a simple sckets-based File Service in Java Server listens n TCP prt Serves Clients ne by ne, serially Main tcl functins fr nw we will extend it File uplad File dwnlad Exercise cnsists f cmpleting and adapting the vided sftware Tday: Get familiar with the sftware vided Study the file uplad cmmand then Implement the file dwnlad cmmand by using FileInputStream and FileOutputStream in CmmandDispatcher.java Next Mnday: Prvide a multithreaded implementatin f the server Study the advantages f multithreading, try t estimate the server s thrughput increase 9 OCTUBRE

11 BASIC LABORATORY EXERCISE (TODAY) Dwnlad surce surce cde frm: palalt.unilen.es/asd/asdfileservice.zip Setup and Cmpile ject accrding t java package name (asdfileservice.server and asdfileservice.client): Run server with parameters (prt and 0) $ java asdfileservice.server.fileserverdriver Then, extend UpladClient.java s such that it retrieves the server IP and prt frm the cmmand line, then run UpladClient, which, will cnnect and send file /tmp/anyfile t the server Server will hnr this request (Observe the peer-t-peer tcl messages interchanged between cleint and server) Nw, yur task cnsists f writing the file dwnlad methd FileOutputStream, new file n server 9 OCTUBRE

12 ADVANCED LABORATORY EXERCISE (NEXT SESSION) Obtain a multithreaded implementatin f the server Design an experimental setup t cmpare the thrughput in singlethreaded vs. Thrughput multithreaded 9 OCTUBRE

Practical Exercises in Computer Networks and Distributed Systems

Practical Exercises in Computer Networks and Distributed Systems (V..6, Nv 2) Practical Exercises in Cmputer Netwrks and Distributed Systems Stream Sckets and the Client/Server mdel (C language, W) 2-, Jsé María F Mrán This practical illustrates basic cncepts prtcl