CS 10: Problem solving via Object Oriented Programming. Client/Server

Transcription

1 CS 10: Problem solving via Object Oriented Programming Client/Server

2 Agenda 1. Sockets 2. Server 3. MulAthreaded server 4. Chat server 2

3 Sockets are a way for computers to communicate IP: HTTP Port: 80 Server Server is listening on a socket (socket = address + protocol + port) Client 1 Client 1 makes connecaon over socket Server receives connecaon, moves communicaaons to own socket Port 80 = HTTP 3

4 Sockets are a way for computers to communicate IP: HTTP Port: 80 Server Server is listening on a socket (socket = address + protocol + port) Port 80 = HTTP Client 1 Client 1 makes connecaon over socket Server receives connecaon, moves communicaaons to own socket Server returns to listening Server talking to Client 1 and ready 4 for others

5 Sockets are a way for computers to communicate IP: HTTP Port: 80 Client 1 Client 2 makes connecaon over socket Server Server is listening on a socket (socket = address + protocol + port) Client 2 Port 80 = HTTP 5

6 Sockets are a way for computers to communicate IP: HTTP Port: 80 Server Server is listening on a socket (socket = address + protocol + port) Port 80 = HTTP Client 1 Client 2 Client 2 makes connecaon over socket Server receives connecaon, moves communicaaons to own socket Server returns to listening Server talking to client 1 and 2 6 ready for others

7 Java provides a convenient Socket class to communicate with servers WWWSocket.java 7

8 Java provides a convenient Socket class to communicate with servers WWWSocket.java Use scanner to read loca3on on CS web server from which user wants to get data String page read from keyboard by scanner Socket: Address Port Protocol Don t forget to close up Open Socket to CS web server on port 80 (standard hbp port) Write out (out from your computer) over Socket to CS web server Read data in from CS web server over Socket into BufferedReader Outputs course web page HTML 8

9 Agenda 1. Sockets 2. Server 3. MulAthreaded server 4. Chat server 9

10 DEMO HelloServer.java: create our own server that listens for clients to connect HelloServer.java Run HelloServer.java Fom terminal type telnet localhost 4242 Quit telnet session with Control + ] then type quit Try connecang from mulaple terminals 10

11 We can create our own server that will listen for clients to connect and respond HelloServer.java Create new ServerSocket listening on port 4242 Port chosen because nothing else there IP: localhost TCP Port: 4242 Pause here un3l someone connects, then create Socket sock for them Server Create output writer and input reader using sock Send output to whomever connected Close up Reader and writer Sockets Read input from client un3l client hangs up (connec3on lost) in.readline() is null on hang up 11

12 We can also create our own client too HelloServer.java and HelloClient.java What is input and what is output is rela3ve to each computer Input to Server is output from Client Output from Server is input to client Code for HelloServer on last slide 12

13 DEMO HelloClient.java: our Client that talks to our Server HelloClient.java Run HelloClient.java (waits for Server to come up) Run HelloServer.java 13

14 Our Client talks to our Server HelloClient.java Setup scanner to read client s keyboard Loop un3l Server answers Output to console what the Server said Create Socket sock on same port as Server (4242) sock will throw excep3on if Server not up, try every 5 seconds un3l it is up Client Got Server connec3on, setup reader and writer Get input from scanner and send to Server If Server hangs up, don t know it un3l you press enter on keyboard. Why? console.nextline() blocks execu3on 14

15 Friends can connect to your server if they connect to the right IP address Run MyIPAdressHelper.java to get your address, edit HelloClient.java Local network router gives inside computers a unique local IP address (e.g., ) Network Address Transla3on (NAT) on local router tells outsiders each inside machine has a different IP address (global address) from what IP address insiders see (e.g., )

16 DEMO: ConnecAng from another machine HelloServer.java and HelloClient.java Run MyIPAddressHelper on server to get IP Start HelloServer.java on server Edit HelloClient.java to change localhost to server IP address Run HelloClient on client machines and make connecaon Connect from student machine? 16

17 Agenda 1. Sockets 2. Server 3. MulAthreaded server 4. Chat server 17

18 Currently our server can only handle one client at a Ame Using Java s Thread mechanism to overcome single client issue We would like our server to talk to mulaple clients at the same Ame (called concurrent users) Trick is to give each client its own socket That way the server can talk concurrently with mulaple clients Java provides a Thread class to handle concurrency (mulaple processes running at same Ame) Threads are much lighter than running mulaple instances of a program (more on threads next class) Inherit from Thread class and override run method Start thread using start method (calls run method) 18

19 We can create a Communicator on a separate thread for each connecaon One Communicator allocated for a single client Communicator Object handles the socket between Server and Client 19

20 We can create a Communicator on a separate thread for each connecaon Mul3ple Communicators allocated for mul3ple clients Create a new Communicator Object on a separate Thread on the server One Communicator for each Client 20

21 DEMO HelloMulAthreadedServer.java: handle mulaple Clients concurrently HelloMul3threadedServer.java Starts new thread with new HelloServerCommunicator on each connecaon HelloServerCommunicator.java Extends Thread Override run Tracks thread ID Otherwise the same as single threaded version Run HelloMul3threadedServer.java with mul3ple telnets 21

22 By using Threads, one Server can handle mulaple concurrent Clients HelloMul3threadedServer.java Create a ServerSocket to listen for incoming connec3ons num keeps track of how many connec3ons have been made Loop forever Put new connec3ons on their own Thread with Communicator setdaemon(true) means stop this Thread when the main Thread ends start() causes a Thread to begin running in Thread Object s run() method Big idea: start a new thread whenever a client connects so this thread can go back to listening for new clients Block un3l Client connects, then return new Socket Pass new ServerSocket on port 4242 to constructor Then call getconnec9ons() 22

23 HelloServerCommunicator runs on its own Thread, handles one Client s connecaon HelloServerCommunicator.java Extends Thread When start() called on Thread, it calls Thread s run() method Save socket to talk to Client and keep id for convenience Print id number so we can track who is communica3ng Setup run() to func3on the same as single- threaded version Now this Thread runs independently of other Threads Handles one Client connec3on Stops when main Thread stops (daemon true) 23

24 Agenda 1. Sockets 2. Server 3. MulAthreaded server 4. Chat server 24

25 DEMO: Chat applicaaon ChatServer.java and ChatClient.java Run MyIPAddressHelper on server to get IP Start ChatSever.java on server Edit ChatClient.java to change localhost to server IP address (in main()) Run ChatClient.java to connect to ChatServer Run ChatClient.java from student machine? 25

26 Goal: Chat server allows communicaaon between mulaple clients Client sends message to server When one Client sends a message, want to broadcast it to all other clients Server coordinates messages Server receives message from Client, then repeats message to all other Clients Message 26

27 Goal: Chat server allows communicaaon between mulaple clients Server broadcasts message to all clients What if a message comes into a Client that is blocking wai3ng for input from keyboard Would like to see message displayed even if typing (or not) Message Message 27

28 Client listens for keyboard on main thread creates Communicator on second thread Client Client uses two threads: 1. Listen for keyboard input (blocks Thread un3l Enter key pressed) 2. Communicates with server on separate Thread (does not block wai3ng for keyboard input) 28

29 ChatServer creates a Communicator for each client Server Both Server and Client side are now mul3- threaded 29

30 ChatServer handles mulaple clients and broadcasts message to each client Client and server Server has one Thread per Client Each Client has two threads 30

31 ChatServer manages one Communicator for each Client ChatServer.java Set up ServerSocket to listen for Client connec3ons Server Communicators Communicator Client Create one Communicator for each Client Keep Communicators in comms ArrayList Set daemon, start Thread running, add to comms Arraylist Block un3l Client connec3on, then create new Communicator running on its own Thread Returns new socket for this Communicator Also pass reference to this Object Add or remove Communicator Object from comms ArrayList 31

32 ChatServer manages one Communicator for each Client ChatServer.java Synchronized keyword makes sure that if two messages arrive at the same 3me, that broadcast finishes the first message before the second Topic of next class Communicators Communicator Client Server Clients will ask Server to broadcast message to all Clients, loop over each Communicator (except Client that sent message) and ask it to send a message to its Client main() set up ServerSocket listening on port

33 Each ChatServerCommunicator runs on own Thread and talks with one Client ChatServerCommunicator.java Extend Thread to run in own thread Communicators Server Communicator Client Save socket to communicate with Client Save ChatServer to communicate with ChatServer Object (e.g., call broadcast()) run() called when Thread is started Set up in reader and out writer as before On any input from Client, call broadcast() on Server broadcast() on Server will call send() on each Communicator (next slide) When Client hangs up, call removecommunicator() on Server and shut down this Thread 33

34 Each ChatServerCommunicator runs on own Thread and talks with one Client ChatServerCommunicator.java Server Communicators Communicator Client When another Client sends a message to the Server via broadcast() method, the Server will call send() on each Communicator to broadcast the message to all Clients 34

35 ChatClient manages keyboard input and creates a ChatClientCommunicator ChatClient.java Set up scanner for keyboard input Communicators Server Communicator Client Create Communicator on another Thread (so not stopped by blocking scanner), start Thread running While Server is connected, tell Communicator to send keyboard messages to Server If Server hangs up, Communicator will call this method to inform ChatClient Object main() calls constructor passing socket on localhost port 4242 then handleuser() 35

36 ChatClientCommunicator runs on its own Thread to communicate with Server ChatClientCommunicator.java Run on own Thread so not blocked by scanner Communicators Server Communicator Client Save socket to communicate with ChatServer Save client to communicate with ChatClient Object Send keyboard message passed by ChatClient Object to Server Read data from ChatServer and write to console If ChatServer hangs up, tell ChatClient Object, then end Thread 36

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