You will need to add a few extra imports for this code. The listener we create that processes the packets simply prints out the packet information. The last step is to tell the open device to loop and process packets using the listener we defined. We will do a few things here, first we will open the device with openLive() and then we will create a PacketListener that defines how to handle the packets when they are received. In this next code snippet, we will modify the main() function to actually open the device that was chosen. Once you have selected a device, you can create call openLive() to create a handle that can be used to listen for packets. Uber-$ Getting a handle and capturing live packets While we're at it, let's tell the compiler plugin to target Java version 1.8. Modify the pom.xml in the root directory of the project and add a section for build and add the following plugin configurations to your existing pom.xml. To make packaging and running the application easier, we should package the application as a JAR with all the dependencies embedded. Now that we have some code we actually want to run and test, let's set up Maven to package our app in to an executable JAR file with dependencies that is ready for us to run. List the network devices available with a promptÄevice = new NifSelector().selectNetworkInterface() and choosing a network interface from the terminal Pcap4j comes with a convenient method for listing The class that will store the network device Update the code to look more like this: // App.java Let's modify the App.java file a bit and put some code in the main() function that will list the network interfaces and ask the user to choose one. It should already look something like this: // App.java Inside the src/main/java directory, drill down the directories until you get to the App.java file. Now we are ready to start writing source code. Inside the created directory, edit the pom.xml file and add a new dependency entry for pcap4j. This will create a pcap directory with a pom.xml file and a src directory. Mvn archetype:generate -DgroupId= -DartifactId=pcap -Dversion=1.0.0 -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false Generate a quickstart project with the following command: # This is all one line I will use Maven to generate a skeleton project that is ready to go. Setting up the project with maven Generate project structure using maven-archetype-quickstart If you prefer to download the JAR and manage the dependencies yourself, you can download the latest JAR from the pcap4j GitHub release page. If you are unfamiliar with Maven or don't have it installed yet, I recommend you first read my tutorial on Maven Basics for Java Developers. In this tutorial we will use Maven and the Maven Central Repository to take care of our Java dependencies, so you don't have to worry about downloading anything manually. We will use the pcap4j Java library to hook in to the native libpcap or WinPcap. If using Windows, you need to install WinPcap which provides a simple installer. Absolute worst case, you will need to build it yourself from source from. On Linux and Mac, libpcap is typically included by default, and if not, most distributions provide a package for easy installation. You need a packet capturing library installed. On Mac and other platforms, I recommend using the Oracle JDK installer from Oracle's JDK download page. On Debian and Ubuntu based distributions, you can instal JDK 8 easily with: sudo apt install openjdk-8-jdk For instructions on installing the JDK on Windows, refer to my tutorial on Installing JDK 1.8 and 9 in Windows. If you have an interest in Go, you can read Packet Capture, Injection, and Analysis with Gopacket or watch my talk from GopherCon 2016: Packet Capture, Analysis, and Injection with Go on YouTube. If you want to learn how to use the underlying pcap library in C, refer to Using libpcap in C. I have a few other packet capturing tutorials in other languages as well. This tutorial will cover packet capturing in the Java programming language using the pcap4j library. Getting a handle and capturing live packets.
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