Network programming 14/01/2013. Introduction. Session objectives. Client/Server working model. Advanced Java Programming Course

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Industrial University f H Chi Minh City Wrking with Scket cnnectin-based prtcl

1 Advanced Java Prgramming Curse Netwrk prgramming Sessin bjectives Netwrking intrductin URL Class InetAddress Class By Võ Văn Hải Faculty f Infrmatin Technlgies Industrial University f H Chi Minh City Wrking with Scket cnnectin-based prtcl cnnectinless-riented prtcl Remte Methd Invcatin (RMI) 2 Client/Server wrking mdel Intrductin 3 4 1

. The varius prtcls are ften categrized in Layers TCP IP TCP is a stream-based prtcl ver IP TCP prmises a reliable transprt TCP takes care f packet rdering, packet lss and data crruptin.

2 Internet architecture: Prtcls & Layers TCP/IP Overview Internet architecture based n Internet prtcl suite cncept als called TCP/IP suite. TC/IP suite cntains many prtcls SMTP, HTTP, FTP, BitTrrent, POP3, UDP, IRC, SNMP, TCP, IP, Wi-Fi.. The varius prtcls are ften categrized in Layers TCP IP TCP is a stream-based prtcl ver IP TCP prmises a reliable transprt TCP takes care f packet rdering, packet lss and data crruptin. A TCP stream is a cnnectin. IP is a prtcl fr cnnecting netwrks IP is a packet-based prtcl Packets can be drpped, garbled r re-rdered and duplicated: IP prmises nthing but best-effrt delivery IP usually runs ver ethernet, but nt always 5 6 TCP/IP Overview TCP ver IP IP Header IP Data Hw Cmputers Cmmunicate When tw applicatins (A and B) n remte machines want t cmmunicate with each ther TCP Header TCP Data Using TCP A cntacts B and wait fr B s respnse If B agree, will then respnd t A (a cnnectin is established) Src Dst Type: TCP Src Prt Dst Prt Seq Num Applicatin Data A & B nw can send data back and frth ver that cnnectin. Using UDP A nly needs t knw B's address. A send data t B (d nt care B is available r nt) 7 8 2

Netwrking Applicatin Basics Hst & Internet Address Netwrking Applicatin Basics Cncept f Prts Hst Devices cnnected t the Internet are called hsts Mst hsts are cmputers, but hsts als include ruters,

This is written in dtted quad frmat like 199.1.32.90 where each byte is an unsigned integer between 0 and 255.

3 Netwrking Applicatin Basics Hst & Internet Address Netwrking Applicatin Basics Cncept f Prts Hst Devices cnnected t the Internet are called hsts Mst hsts are cmputers, but hsts als include ruters, printers, fax machines, sda machines, bat huses, etc. Internet addresses Every hst n the Internet is identified by a unique, fur-byte Internet Prtcl (IP) address. This is written in dtted quad frmat like where each byte is an unsigned integer between 0 and 255. There are abut fur billin unique IP addresses, but they aren t very efficiently allcated A cmputer generally has a single physical cnnectin available fr the netwrk. Several applicatins running n a machine need t use this single physical cnnectin fr cmmunicatin. If data arrives at these physical cnnectins, there is n means t identify the applicatin t which it shuld be frwarded. Hence, data being sent and received n the physical cnnectin are based n the cncept f prts Netwrking Applicatin Basics Cncept f a Prts The physical cnnectin is lgically numbered within a range f 0 t called as Prts. The prt numbers ranging frm 0 t 1023 are reserved fr well knwn services such as HTTP, FTP Yur applicatins shuld nt use any f the prt numbers in this range. Data transmitted ver the Internet is accmpanied with the destinatin address and the prt number. The destinatin address identifies the cmputer The prt number identifies the applicatin. The InetAddress Class The InetAddress represents an Internet Prtcl (IP) address It retrieves the hst address/name. It prvides methds t reslve hst names t their IP addresses and vise versa

4 URL The URL class A URL, shrt fr "Unifrm Resurce Lcatr", is a way t unambiguusly identify the lcatin f a resurce n the Internet. The resurce can be an HTML page, an image r simply any file. URL frm prtcl://resurce Prtcl Identifier Name f the prtcl, which is used t fetch the resurce frm the Internet. Resurce Name Address f the resurce Separated frm the prtcl identifier with a cln and tw frward slashes Resurce frmat depends n the prtcl being used URL examples file:///macintsh%20hd/java/dcs/jdk% %20dcs/a pi/java.net.inetaddress.html#_tp_ ftp://ftp.inf.apple.cm/pub/ mailt:elhar@metalab.unc.edu telnet://utpia.ply.edu ftp://mp3:mp3@ :21000/c%3a/stuff/mp3/ al+wrks 15 The java.net.url class The URL class represents an URL bject. The URL class cntains methds t create new URLs parse the different parts f a URL get an input stream frm a URL s yu can read data frm a server get cntent frm the server as a Java bject Supprted Prtcls file ftp gpher http mailt appletresurce dc netdc systemresurce verbatim 16 4

Parsing URLs The java.net.url class has five methds t split a URL int its cmpnent parts.

public String getref() 17 18 Reading Data frm a URL URL example The penstream() methd cnnects t the server

public final InputStream penstream() thrws IOExceptin Any headers that precede the actual data are stripped

5 Parsing URLs The java.net.url class has five methds t split a URL int its cmpnent parts. These are: public String getprtcl() public String gethst() public int getprt() public String getfile() public String getref() Reading Data frm a URL URL example The penstream() methd cnnects t the server specified in the URL and returns an InputStream bject fed by the data frm that cnnectin. public final InputStream penstream() thrws IOExceptin Any headers that precede the actual data are stripped ff befre the stream is pened. Netwrk cnnectins are less reliable and slwer than files. Buffer with a BufferedReader r a BufferedInputStream

URLCnnectins The java.net.urlcnnectin class is an abstract class that The URLCnnectin class handles cmmunicatin with different kinds f servers like ftp servers and web servers.

6 URLCnnectins The java.net.urlcnnectin class is an abstract class that The URLCnnectin class handles cmmunicatin with different kinds f servers like ftp servers and web servers. Prtcl specific subclasses f URLCnnectin handle different kinds f servers. By default, cnnectins t HTTP URLs use the GET methd. Capacities: Can send utput as well as read input Can pst dat Can read headers frm a cnnectin URLCnnectin five steps I/O Acrss a URLCnnectin 1. The URL is cnstructed. 2. The URL s pencnnectin() methd creates the URLCnnectin bject. 3. The parameters fr the cnnectin and the request prperties that the client sends t the server are set up. Data may be read frm the cnnectin in ne f tw ways raw by using the input stream returned by getinputstream() thrugh a cntent handler with getcntent(). Data can be sent t the server using the utput stream prvided by getoutputstream(). 4. The cnnect() methd makes the cnnectin t the server. 5. The respnse header infrmatin is read using getheaderfield()

HTML n Cmpnents HTML in Swing Mst text-based Swing cmpnents, such as labels,

HTML. The cmpnent will display it apprpriately.

2 renderer that can handle frames, frms, hyperlinks, and parts f CSS Level 1.

7 HTML n Cmpnents HTML in Swing Mst text-based Swing cmpnents, such as labels, buttns, menu items, tabbed panes, and tl tips, can have their text specified as HTML. The cmpnent will display it apprpriately The JEditrPane class This class prvides an even mre cmplete HTML 3.2 renderer that can handle frames, frms, hyperlinks, and parts f CSS Level 1. The JEditrPane class als supprts plain text and basic RTF The JEditrPane class example Cnstructrs Navigate/Display cntents

8 Implementing server Scket prgramming The Java interface with a TCP cnnectin is a scket. Scket prgramming TCP Scket A scket is a Java bject which has methds t cnnect, accept cnnectins and transfer data. Cre Netwrking is in java.net.* TCP Sckets cme in tw flavrs : ServerScket and Scket Implementing server The ServerScket Class Implementing server The ServerScket Class (cnt.) Represent the server side f the tw-way cmmunicatin. The ServerScket has t bind t a specific prt which shuld be free and available. If the prt is being used by any ther applicatin, an exceptin is thrwn. If the ServerScket class is successful in binding t a prt, it can then wait and listen fr client request t establish cnnectins

Implementing server Wrking with the ServerScket class Once a ServerScket instance is created, yu can invke the accept() methd t listen fr client request.

9 Implementing server Wrking with the ServerScket class Once a ServerScket instance is created, yu can invke the accept() methd t listen fr client request. The accept () methd is a blcking methd that is nce invked it will wait till a client requests fr a cnnectin. When a client requests fr a cnnectin, the accept() methd creates a scket bject f class Scket and returns it. Implementing server Wrking with the Scket class Represent the cnnectin between a client prgram and a server prgram. Represents the client side f the cnnectin This returned bject represents a prxy f a client. T cmmunicate with the client, yu retrieve the Inputstream and Outputstream f this prxy scket bject Implementing server Lgic diagram t implements a server Implementing server Example 1) It gets a cmmand frm the client thrugh an incming data stream. 2) It smehw fetches the infrmatin. 3) It sends the infrmatin t the client thrugh the utging data stream

Implementing server Serving Multiple clients Implementing server Serving Multiple clients example One ServerScket can accept multiple clients simultaneusly. Use multithreading t handle them.

10 Implementing server Serving Multiple clients Implementing server Serving Multiple clients example One ServerScket can accept multiple clients simultaneusly. Use multithreading t handle them. One thread waits fr accept(). Open a new thread fr each cnnectin Fr cnnectin-based prtcl - Scket class Represent the cnnectin between a client prgram and a server prgram. Represents the client side f the cnnectin Implementing client Lgic diagram t implements a client 1) Create a cnnectin t the server 2) Send request infrmatin t the server thrugh the utging data stream. 3) It receives the infrmatin frm the server thrugh the incming data stream. 4) Prcessing received infrmatin 40 FPT- APTECH 40/

11 Implementing client Client example Data transmissin recmmendatins T transmit text nly data, we can use InputStream and OutputStream. T transmit binary data, we must turn the streams int DataInputStream and DataOutputStream. T transmit serialized bjects, we wuld use ObjectInputStream and ObjectOutputStream instead User Datagram Prtcl (UDP) intrductin UDP can be used t send packets. The packets can be delivered in randm rder. It is up t the recipient t put the packets in rder and t request retransmissin f missing packets. User Datagram Prtcl (UDP) Create Datagram Scket DatagramScket scket = new DatagramScket(prt); The client uses a cnstructr that des nt require a prt number. This cnstructr just binds the DatagramScket t any available lcal prt. It desn't matter what prt the client is cnnected t because the DatagramPackets cntain the addressing infrmatin. UDP is mst suited fr applicatins where missing packets can be tlerated, fr example, in audi r vide streams... The server gets the prt number frm the DatagramPackets and send its respnse t that prt

Packet delivery is nt guaranteed Datagram packet structure Addressing infrmatin (IP) Prt Sequence f bytes 46 FPT- APTECH 46/43 47 User

12 User Datagram Prtcl (UDP) The Datagram packet An independent, self-cntained message sent ver the netwrk. User Datagram Prtcl (UDP) The DatagramPacket class Used t emply a cnnectinless packet delivery service. Packet delivery is nt guaranteed Datagram packet structure Addressing infrmatin (IP) Prt Sequence f bytes 46 FPT- APTECH 46/43 47 User Datagram Prtcl (UDP) Hw t use DatagramScket class Once a DatagramScket instance is created, it can be used t send and receive data using packets. User Datagram Prtcl (UDP) Prcessing lgic - Client send Request t Server

13 User Datagram Prtcl (UDP) Prcessing lgic - Server receive Request frm Client User Datagram Prtcl (UDP) Prcessing lgic - Server Sends Respnse The getdata() methd t retrieve that data frm the packet User Datagram Prtcl (UDP) Prcessing lgic Client receive respnse The Multicast Scket?

Remte Methd Invcatin The Rles f Client and Server synchrnized request/respnse mdel 55 Remte Methd call with prxies new apprach The netwrk is the cmputer * Cnsider the fllwing prgram rganizatin: methd

14 Remte Methd Invcatin The Rles f Client and Server synchrnized request/respnse mdel 55 Remte Methd call with prxies new apprach The netwrk is the cmputer * Cnsider the fllwing prgram rganizatin: methd call SmeClass AntherClass returned bject cmputer 1 cmputer 2 If the netwrk is the cmputer, we ught t be able t put the tw classes n different cmputers RMI is ne technlgy that makes this pssible

What is RMI? RMI Architecture RMI allws bjects in ne JVM t invke methds f bjects in anther JVM. All in java.rmi package 1. RMI Server prvides an RMI service. 2.

15 What is RMI? RMI Architecture RMI allws bjects in ne JVM t invke methds f bjects in anther JVM. All in java.rmi package 1. RMI Server prvides an RMI service. 2. RMI Client invkes bject methds f RMI service 3. rmiregistry prgram Runs as a separate prcess Allws applicatins t register RMI services Allws btain a reference t a named service. 4. Stub bject Resides n the client side Respnsible fr passing a message t a remte RMI service, waits fr a respnse, and returns this respnse t the client Stubs Parameters marshalling When client cde wants t invke a remte methd n a remte bject, it actually calls an rdinary methd f the Java prgramming language that is encapsulated in a surrgate bject called a stub. The stub packages the parameters used in the remte methd int a blck f bytes. This packaging uses a device-independent encding fr each parameter. The prcess f encding the parameters is called parameter marshalling. The purpse f parameter marshalling is t cnvert the parameters int a frmat suitable fr transprt frm ne virtual machine t anther

Implementing RMI applicatin prcess 1. Define RMI Service Interface 2. Implement RMI Service Interface 3. Create RMI Server prgram 4. Create RMI Client prgram 5.

16 Implementing RMI applicatin prcess 1. Define RMI Service Interface 2. Implement RMI Service Interface 3. Create RMI Server prgram 4. Create RMI Client prgram 5. Running the RMI applicatin #1/5 Define RMI Service Interface Yur client prgram needs t manipulate server bjects, but it desn't actually have cpies f them. Their capabilities are expressed in an interface that is shared between the client and server and s resides simultaneusly n bth machines. The interface characteristics: Must be public Must extend the interface java.rmi.remte Every methd in the interface must declare that it thrws java.rmi.remteexceptin (ther exceptins may als be thrwn) #2/5 Implementing RMI Service Interface #3/5 Creating RMI Server prgram On the server side, yu must implement the class that actually carries ut the methds advertised in the remte interface The class characteristics: Shuld extend java.rmi.server.unicastremteobject Must implement a Remte interface Must have a default cnstructr. The RMI server is respnsible fr: 1. Instance bject f a service implementatin class 2. Registering it with the RMI registry

#4/5 Creating RMI Client prgram #5/5 Running the RMI System The client btains an bject reference t the remte interface by making a lkup in the RMI registry Then invking methds f the service interface.

17 #4/5 Creating RMI Client prgram #5/5 Running the RMI System The client btains an bject reference t the remte interface by making a lkup in the RMI registry Then invking methds f the service interface. 66 Start Server Cmpile all java file as nrmal. cmd: javac *.java Start rmiregistry prgram. cmd: start rmiregistry Run server prgram. cmd: start java Calc_Server Start Client Create plicy file cmd: client.plicy Run client cmd: java -Djava.security.plicy=client.plicy Calc_Client 67 Security Others By default, the RMISecurityManager restricts all cde in the prgram frm establishing netwrk cnnectins. Hwever, the prgram needs t make netwrk cnnectins T reach the RMI registry; and T cntact the server bjects T allw the client t cnnect t the RMI registry and the server bject, yu supply a plicy file. Here is a plicy file that allws an applicatin t make any netwrk cnnectin t a prt with prt number f at least 1024: grant{ }; permissin java.net.scketpermissin "*: ","cnnect"; Listing all bunded remte bjects in registry Create yur wn RMIRegistry java.rmi.registry.lcateregistry.createregistry(1099);

18 Summary FAQ Data exchange thrugh netwrk using Scket, UDP Remte methd invcatin That s all fr this sessin! Thank yu all fr yur attentin and patient! /27 18

CCNA 1 Chapter v5.1 Answers 100%

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