How to interpret packets?

Replies

• 

  Manish Goyal

  guys i have achieved what i want 😀 I have used 2nd method ie callback method for this
  
  but still confused why there was exception in first case when i try to capture packets one by one
• 

  durga ch

  did you try to goggle then with the error message you received?
  
  To interpret packets may be you can refer to this thread #-Link-Snipped-#
• 

  Manish Goyal

  yeah i had searched on google about this ..
  But the error was same that i commonly encountered during programming in java
  
  ie null
• 

  Manish Goyal

  Now again there is new problem
  
  Previously when i was using my broadband connection for accessing internet .I was able to capture packets, received by my system.
  
  but now when i am accessing internet using my mobile as a modem(usb modem) ,i am not able to see even single packet .
  
  can anyone explain me what's the reason?
• 

  durga ch

  USB port numbers are different from your Ethernet port number right?
  can you explain your program above? I am a JAVA illeterate
• 

  Manish Goyal

  I have used jpcap which is a open source library for capturing and sending packets from java applications
  
  To get the List of network Interfaces of my machine.jpcap provides JpcapCaptor.getDeviceList() method which is static method of JpcapCaptor class.It will return array of NetworkInterface objects and by using the fields of NetworkInterface class ,I can retrieve each and every information of networkinterface of my machine.
  
  JpcapCaptor captor=JpcapCaptor.openDevice(device[index], 65535, false, 20);
  
  Once we obtain the list of network interfaces and choose which network interface to capture packets from, you can open the interface by
  using jpcap.opendevice() method
  
  while calling openDevice(),we provide following parameters
  NetworkInterface interface:-NetworkInterface which you want to open
  int no:-Max no of bytes to cpature
  boolean promics :-Whether to open device in promiscuous mode or not
  int time_out:-to set capture time_out value
  
  Once you obtain an instance of of jpcapcaptor,you can capture packets from the interface.
  
  There are two major approaches to capture packets using a #-Link-Snipped-#
  instance: using a callback method, and capturing packets one-by-one
  
  In callback method we implement the interface named PacketReceiver then create a method named which will handle the packets gernerated
  
  For capturing packets we can use either processPacket() or loopPacket() method.
  
  For each captured packet it will call the method which i have created to handle that packet
  
  and in one by one approach .I will simply create a loop and capture packets by using getPacket() method
  
  I hope,you got an idea
  
  If still confused then post your query
• 

  durga ch

  alright
  By what you have said - since its our network interface device has changed < i think the problem might be here
  "while calling openDevice(),we provide following parameters
  NetworkInterface interface:-NetworkInterface which you want to open
  int no:-Max no of bytes to cpature
  boolean promics :-Whether to open device in promiscuous mode or not
  int time_out:-to set capture time_out value"
  
  this is a just a inference though.
• 

  Manish Goyal

  But when i execute my program there is only one networkInterface it is showing on output, which i can open
• 

  durga ch

  ..and which network interface does it show?
• 

  Manish Goyal

  VIA RHINE II Fast Ethernet Adapter
• 

  Manish Goyal

  I think the problem is with net connection .I am not sure whether this program works on dial up connection or not