Introduction to Network Programming in Java

Transcription

1 Introduction to Network Programming in Java Regarding assignments in the Computer Networks course 1DV201 Created by Marcus Edvinsson Maintained by Oleg Danylenko

2 Download Sources Download source files to local machine UDPEchoServer.java UDPEchoClient.java Remember where you put them on the local file system. We assume that you have downloaded them to P:\dv201

3 Eclipse Open Eclipse Create new Java project We assume you name it dv201 Right-click the project dv201 Choose Properties Choose Resource The field Location tells us where the project files are located on the file system We assume this is P:\dv201\eclipse\dv201

4 Eclipse Move the.java files from P:\dv201 to P:\dv201\eclipse\dv201\src in a file manager, e.g., Explorer Change to Eclipse Right click the Java project dv201 Choose Refresh The files now show up below the src folder Open the UDPEchoClient class If package dv201.labb2 is marked red the class is located in the wrong place in the file system. To fix the error do the following: Click the error marker to the right Double click Move UDPEchoClient to The UDPEchoClient class is moved to the dv201.labb2 package Repeat for the UDPEchoServer class

5 Running in Eclipse For the client to work, we have to give it arguments Choose menu option Run Choose option Open Run Dialog (Could be named differently in other Eclipse versions) If there is an appropriate run profile for your program, mark this Otherwise Right click Java Applications Choose New Choose tab Arguments In Program Arguments: give your arguments For running the server on the local machine and connect the client to it we give the arguments localhost 4950 localhost is the name of the local machine, for connecting to other machines write the name of the machine, e.g., 1DV201.msi.vxu.se 4950 is the port number the server listens to Could be found in the static field MYPORT in the server source code

6 Consoles in Eclipse When running the client and the server we get two output consoles These are shown in the View Console We can switch between these two in the Console view using the button Display Selected Console When an application is running square named Terminate shows Click this to terminate the running program

7 Connect to UNIX machines When connect to a UNIX machine, use the PuTTy program Find its download site by Google PuTTy download When starting PuTTy use any of these host names: 1dv201a.msi.vxu.se 1dv201b.msi.vxu.se You can start multiple PuTTy sessions to one or many UNIX machines at the same time

8 Home Folder When you login to the Windows machines you get access to P:, which is your home folder This is also accessible from the UNIX machines Copying files to P: makes them available on the UNIX machines This means that all UNIX machines also share the same folder

9 Home Folder To run Java programs on UNIX machines we need to make sure that we have the class files on our P: If you are NOT using P: to store your Eclipse project, we need to copy the class files to P: We want to have the project on P:, since we are able to change computers and still have access to our files this way If we store the Eclipse project on the local machine, e.g., the Desktop, C:, etc. they may disappear and we need to use the exact same computer all the time Conclusion login on the machine to get access to P: Store your Eclipse project on P: This makes everything much easier!!!

10 Running from Terminal Window In the Eclipse project dv201 folder we have at least two folders - src and bin To run an application from this project we need to set the CLASSPATH environment variable to make sure the Java VM can find the class files On UNIX machines we change the current working directory to the bin folder of the dv201 project using the cd command Issue the command pwd and the terminal prints the current working directory If the user meddv98 would do this the result would be /stud/1998/dv/med/dv201/eclipse/dv201/bin The path to the home folder of the user meddv98 is /stud/1998/dv/med The following part of the path is the location of the bin folder of the dv201 Eclipse Java project, i.e., the path on P: (P:\dv201\eclipse\dv201) Issue the command: export CLASSPATH= <path> Change <path> to the result of the pwd command above Continuing the example with the user meddv98 the command would be: export CLASSPATH= /stud/1998/dv/med/dv201/eclipse/dv201/bin This has to be done for each time you open a PuTTy terminal window, since it is not stored anywhere. It is possible to store it, but that is left to you to find out how. It is left out of the scope of this manual

11 Running from Terminal Window We are now ready to start running Java programs To start the UDPEchoServer Java application we could write /opt/java/jdk1.5.0_04/bin/java dv201.labb2.udpechoserver

12 Summary Use P: for storing your Eclipse project Use PuTTy to connect to UNIX machines Set CLASSPATH environment variable Use Suns Java documentation for information about methods and classes