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  • Reading UDP Packets

    - by Thomas Mathiesen
    I am having some trouble dissecting a UDP packet. I am receiving the packets and storing the data and sender-address in variables 'data' and 'addr' with: data,addr = UDPSock.recvfrom(buf) This parses the data as a string, that I am now unable to turn into bytes. I know the structure of the datagram packet which is a total of 28 bytes, and that the data I am trying to get out is in bytes 17:28. I have tried doing this: mybytes = data[16:19] print struct.unpack('>I', mybytes) --> struct.error: unpack str size does not match format And this: response = (0, 0, data[16], data[17], 6) bytes = array('B', response[:-1]) print struct.unpack('>I', bytes) --> TypeError: Type not compatible with array type And this: print "\nData byte 17:", str.encode(data[17]) --> UnicodeEncodeError: 'ascii' codec can't encode character u'\xff' in position 0: ordinal not in range(128) And I am not sure what to try next. I am completely new to sockets and byte-conversions in Python, so any advice would be helpful :) Thanks, Thomas

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  • What's the cause of (and treatment for) this java MySQL exception?

    - by justkevin
    I'm getting the following exception when executing the first preparedstatement after a period of inactivity: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure The last packet successfully received from the server was 2,855,054 milliseconds ago. The last packet sent successfully to the server was 123 milliseconds ago. at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) at java.lang.reflect.Constructor.newInstance(Unknown Source) at com.mysql.jdbc.Util.handleNewInstance(Util.java:406) at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1074) at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3052) at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2938) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3481) at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1959) at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2109) at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2648) at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2077) at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:2228) This only shows up if my application hasn't communicated with MySQL recently. Subsequent queries execute normally. I suspect it's some kind of timeout issue, but the periods of inactivity are way below the 8 hour timeout for MySQL. Any suggestions?

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  • Why do socket.makefile objects fail after the first read for UDP sockets?

    - by Eli Courtwright
    I'm using the socket.makefile method to create a file-like object on a UDP socket for the purposes of reading. When I receive a UDP packet, I can read the entire contents of the packet all at once by using the read method, but if I try to split it up into multiple reads, my program hangs. Here's a program which demonstrates this problem: import socket from sys import argv SERVER_ADDR = ("localhost", 12345) sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) sock.bind(SERVER_ADDR) f = sock.makefile("rb") sock.sendto("HelloWorld", SERVER_ADDR) if "--all" in argv: print f.read(10) else: print f.read(5) print f.read(5) If I run the above program with the --all option, then it works perfectly and prints HelloWorld. If I run it without that option, it prints Hello and then hangs on the second read. I do not have this problem with socket.makefile objects when using TCP sockets. Why is this happening and what can I do to stop it?

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  • How can I make an "abstract" enum in a .NET class library?

    - by Lazlo
    I'm making a server library in which the packet association is done by enum. public enum ServerOperationCode : byte { LoginResponse = 0x00, SelectionResponse = 0x01, BlahBlahResponse = 0x02 } public enum ClientOperationCode : byte { LoginRequest = 0x00, SelectionRequest = 0x01, BlahBlahRequest = 0x02 } That works fine when you're working in your own project - you can compare which enum member is returned (i.e. if (packet.OperationCode == ClientOperationCode.LoginRequest)). However, since this is a class library, the user will have to define its own enum. Therefore, I have two enums to add as "abstract" - ServerOperationCode and ClientOperationCode. I know it's not possible to implement abstract enums in C#. How would I go doing this?

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  • Programmatic resource monitoring per process in Linux

    - by tuxx
    Hi, I want to know if there is an efficient solution to monitor a process resource consumption (cpu, memory, network bandwidth) in Linux. I want to write a daemon in C++ that does this monitoring for some given PIDs. From what I know, the classic solution is to periodically read the information from /proc, but this doesn't seem the most efficient way (it involves many system calls). For example to monitor the memory usage every second for 50 processes, I have to open, read and close 50 files (that means 150 system calls) every second from /proc. Not to mention the parsing involved when reading these files. Another problem is the network bandwidth consumption: this cannot be easily computed for each process I want to monitor. The solution adopted by NetHogs involves a pretty high overhead in my opinion: it captures and analyzes every packet using libpcap, then for each packet the local port is determined and searched in /proc to find the corresponding process. Do you know if there are more efficient alternatives to these methods presented or any libraries that deal with this problems?

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  • Converting from ANSI to Unicode

    - by Rayne
    Hi all, I'm using Visual Studio .NET 2003, and I'm trying to convert a program written in purely ANSI characters to be independent of Unicode/Multi-byte characters. The program has a callback function of pcap_loop, called "got_packet". It's defined as void got_packet(u_char *user, const struct pcap_pkthdr *header, const u_char *cpacket) { USES_CONVERSION; _TUCHAR *packet; packet = A2T(cpacket); ... } However, I get the error message error C2440: 'type cast': cannot convert from 'const u_char *' to 'ATL::CA2WEX<>' How do fix this? Thank you. Regards, Rayne

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  • GKSession sendDataToAllPeers including sender?

    - by Typeoneerror
    I've got a number of devices connected over wifi using GameKit. I have a simple UIAlertView popping up when peers receive data. All but the sendee show this alert view when data is sent, so I'm wondering if that's a bug in my app or if that's expected behavior. If the device doing the sending is also a GKSessionModePeer, I would expect it to "fire" its receiveData: message as well since I'm sending to all peers. Should I call a method manually at the same on the sendee device? For example, if I wanted to send a "GameStart" packet to the 4 phones, the peers would call startGame: in the receiveData:fromPeer:inSession:context: method when it receives that packet and the sendee would be calling sendDataToAllPeers: and call startGame: on itself. Does that sound right or is there a way to include the sendee in the sendDataToAllPeers: list so that it responds exactly the same as all connected peers?

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  • Last in First out UDP structure in MatLab.

    - by D Zondervan
    I am using MatLabs UDP function in their instrument control toolbox to send data packets from one computer to another. The first computer is constantly updating data values and sending them to the other computer, and I want that computer to be able to query the first one for the most recent values whenever it needs them. However, the default implementation of the UDP send and receive in MatLab is a FIFO structure- the first packet I send is the first the other computer receives when they execute the "fscanf" function. I want the last packet I sent to be the one the fscanf function returns. Is this possible or do I need to use a different protocol?

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  • Loop through hex variable in C

    - by Jud Stephenson
    I have the following code in a project that write's the ascii representation of packet to a unix tty: int written = 0; int start_of_data = 3; //write data to fifo while (length) { if ((written = write(fifo_fd, &packet[start_of_data], length)) == -1) { printf("Error writing to FIFO\n"); } else { length -= written; } } I just want to take the data that would have been written to the socket and put it in a variable. to debug, I have just been trying to printf the first letter/digit. I have tried numerous ways to get it to print out, but I keep getting hex forms (I think). The expected output is: 13176 and the hex value is: 31 33 31 37 36 0D 0A (if that is even hex) Obviously my C skills are not the sharpest tools in the shed. Any help would be appreciated.

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  • How does one capture H.323 voice traffic on a VOIP network?

    - by Chris Holmes
    What I am trying to do is capture the WAV data of a phone conversation on a VOIP network using SharpPCap/PCap.Net. We are using the H.323 recommendation and my understanding is that voice data is located in the RTP packets. However, there is no way to heuristically determine if a UDP packet is a RTP packet, so we have to do more work before we can capture the data. The H.323 recommendation apparently uses a lot of traffic on specific TCP ports to negotiate the call before the WAV data is sent via RTP. However, I am having very little luck determining what data is actually sent on those TCP ports, when it is sent, what the packets look like, how to handle it, etc. If anyone has any information on how to go about this I'd really appreciate it. My Google-Fu seems to be failing me on this one.

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  • how do I get the IP of incoming ICMP due to UDP-send to dead client in Ruby?

    - by banister
    so.. I'm doing a small multiplayer game with blocking UDP and IO.select. To my problem.. (In the server) reading from a UDP socket (packet, sender = @socket.recvfrom(1000)) which have just sent a packet to a dead client results in a ICMP unreachable (and exception Errno::ECONNRESET in ruby). The problem is that I can't find any way whatsoever to extract the IP of that ICMP.. so I can clean out that dead client. Anyone know how to achieve this? thanks

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  • Why do I get a nullpointerexception at line ds.getPort in class L1?

    - by Fred
    import java.awt.; import java.awt.event.; import javax.swing.; import java.io.; import java.net.; import java.util.; public class Draw extends JFrame { /* * Socket stuff */ static String host; static int port; static int localport; DatagramSocket ds; Socket socket; Draw d; Paper p = new Paper(ds); public Draw(int localport, String host, int port) { d = this; this.localport = localport; this.host = host; this.port = port; try { ds = new DatagramSocket(localport); InetAddress ia = InetAddress.getByName(host); System.out.println("Attempting to connect DatagramSocket. Local port " + localport + " , foreign host " + host + ", foreign port " + port + "..."); ds.connect(ia, port); System.out.println("Success, ds.localport: " + ds.getLocalPort() + ", ds.port: " + ds.getPort() + ", address: " + ds.getInetAddress()); Reciever r = new Reciever(ds); r.start(); } catch (Exception e) { e.printStackTrace(); } setDefaultCloseOperation(EXIT_ON_CLOSE); getContentPane().add(p, BorderLayout.CENTER); setSize(640, 480); setVisible(true); } public static void main(String[] args) { int x = 0; for (String s : args){ if (x==0){ localport = Integer.parseInt(s); x++; } else if (x==1){ host = s; x++; } else if (x==2){ port = Integer.parseInt(s); } } Draw d = new Draw(localport, host, port); } } class Paper extends JPanel { DatagramSocket ds; private HashSet hs = new HashSet(); public Paper(DatagramSocket ds) { this.ds=ds; setBackground(Color.white); addMouseListener(new L1(ds)); addMouseMotionListener(new L2()); } public void paintComponent(Graphics g) { super.paintComponent(g); g.setColor(Color.black); Iterator i = hs.iterator(); while(i.hasNext()) { Point p = (Point)i.next(); g.fillOval(p.x, p.y, 2, 2); } } private void addPoint(Point p) { hs.add(p); repaint(); } class L1 extends MouseAdapter { DatagramSocket ds; public L1(DatagramSocket ds){ this.ds=ds; } public void mousePressed(MouseEvent me) { addPoint(me.getPoint()); Point p = me.getPoint(); String message = Integer.toString(p.x) + " " + Integer.toString(p.y); System.out.println(message); try{ byte[] data = message.getBytes("UTF-8"); //InetAddress ia = InetAddress.getByName(ds.host); String convertedMessage = new String(data, "UTF-8"); System.out.println("The converted string is " + convertedMessage); DatagramPacket dp = new DatagramPacket(data, data.length); System.out.println(ds.getPort()); //System.out.println(message); //System.out.println(ds.toString()); //ds.send(dp); /*System.out.println("2Sending a packet containing data: " +data +" to " + ia + ":" + d.port + "...");*/ } catch (Exception e){ e.printStackTrace(); } } } class L2 extends MouseMotionAdapter { public void mouseDragged(MouseEvent me) { addPoint(me.getPoint()); Point p = me.getPoint(); String message = Integer.toString(p.x) + " " + Integer.toString(p.y); //System.out.println(message); } } } class Reciever extends Thread{ DatagramSocket ds; byte[] buffer; Reciever(DatagramSocket ds){ this.ds = ds; buffer = new byte[65507]; } public void run(){ try { DatagramPacket packet = new DatagramPacket(buffer, buffer.length); while(true){ try { ds.receive(packet); String s = new String(packet.getData()); System.out.println(s); } catch (Exception e) { e.printStackTrace(); } } } catch (Exception e) { e.printStackTrace(); } } }

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  • pgp key information

    - by calccrypto
    can someone show a description of the information of what a pgp looks like if only the descriptions were there but not the actual information? something like (i dont remember if the values are correct): packet-type[4 bits], total length in bytes[16 bits], packet version type [4 bits], creation-time[32 bits], encryption-algorithm[8 bits], ...,etc,etc ive tried to understand rfc4880, but its tedious and confusing. so far, i am think i have extracted the 4 i wrote above, but i cant seem to get the rest of the information out. can anyone help? i know i can just find some pgp program, but the whole point of this is to allow me to learn how those programs work in the first place

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  • tracing a linux kernel, function-by function (biggest only) with us timer

    - by osgx
    Hello I want to know, how does the linux kernel do some stuff (receiving a tcp packet). In what order main tcp functions are called. I want to see both interrupt handler (top half), bottom half and even work done by kernel after user calls "read()". How can I get a function trace from kernel with some linear time scale? I want to get a trace from single packet, not the profile of kernel when receiving 1000th of packets. Kernel is 2.6.18 or 2.6.23 (supported in my debian). I can add some patches to it.

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  • Android USB Host Communication

    - by Kip Russell
    I'm working on a project that utilizes the USB Host capabilities in Android 3.2. I'm suffering from a deplorable lack of knowledge and talent regarding USB/Serial communication in general. I'm also unable to find any good example code for what I need to do. I need to read from a USB Communication Device. Ex: When I connect via Putty (on my PC) I enter: >GO And the device starts spewing out data for me. Pitch/Roll/Temp/Checksum. Ex: $R1.217P-0.986T26.3*60 $R1.217P-0.986T26.3*60 $R1.217P-0.987T26.3*61 $R1.217P-0.986T26.3*60 $R1.217P-0.985T26.3*63 I can send the initial 'GO' command from the Android device at which time I receive an echo of 'GO'. Then nothing else on any subsequent reads. How can I: 1) Send the 'go' command. 2) Read in the stream of data that results. The USB device I'm working with has the following interfaces (endpoints). Device Class: Communication Device (0x2) Interfaces: Interface #0 Class: Communication Device (0x2) Endpoint #0 Direction: Inbound (0x80) Type: Intrrupt (0x3) Poll Interval: 255 Max Packet Size: 32 Attributes: 000000011 Interface #1 Class: Communication Device Class (CDC) (0xa) Endpoint #0 Address: 129 Number: 1 Direction: Inbound (0x80) Type: Bulk (0x2) Poll Interval (0) Max Packet Size: 32 Attributes: 000000010 Endpoint #1 Address: 2 Number: 2 Direction: Outbound (0x0) Type: Bulk (0x2) Poll Interval (0) Max Packet Size: 32 Attributes: 000000010 I'm able to deal with permission, connect to the device, find the correct interface and assign the endpoints. I'm just having trouble figuring out which technique to use to send the initial command read the ensuing data. I'm tried different combinations of bulkTransfer and controlTransfer with no luck. Thanks. I'm using interface#1 as seen below: public AcmDevice(UsbDeviceConnection usbDeviceConnection, UsbInterface usbInterface) { Preconditions.checkState(usbDeviceConnection.claimInterface(usbInterface, true)); this.usbDeviceConnection = usbDeviceConnection; UsbEndpoint epOut = null; UsbEndpoint epIn = null; // look for our bulk endpoints for (int i = 0; i < usbInterface.getEndpointCount(); i++) { UsbEndpoint ep = usbInterface.getEndpoint(i); Log.d(TAG, "EP " + i + ": " + ep.getType()); if (ep.getType() == UsbConstants.USB_ENDPOINT_XFER_BULK) { if (ep.getDirection() == UsbConstants.USB_DIR_OUT) { epOut = ep; } else if (ep.getDirection() == UsbConstants.USB_DIR_IN) { epIn = ep; } } } if (epOut == null || epIn == null) { throw new IllegalArgumentException("Not all endpoints found."); } AcmReader acmReader = new AcmReader(usbDeviceConnection, epIn); AcmWriter acmWriter = new AcmWriter(usbDeviceConnection, epOut); reader = new BufferedReader(acmReader); writer = new BufferedWriter(acmWriter); }

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  • make error in re-building ns2

    - by user3702405
    I have implemented a new routing protocol named AODV2 in ns-2.35. I am using ns-2.35 in fedora 13. All .cc files have a .o file with them that means recompilation is done. But I am getting an error in response to the 'make' command. Error is shown below: trace/cmu-trace.o: In function hdr_aodv2::access(Packet const*)': cmu-trace.cc:(.text._ZN9hdr_aodv26accessEPK6Packet[hdr_aodv2::access(Packet const*)]+0x7): undefined reference tohdr_aodv2::offset_2' collect2: ld returned 1 exit status make: * [ns] Error 1 I don't know how to remove this error, Can anyone help me please? Thanks, Naeem

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  • GKSession sendDataToAllPeers including sendee?

    - by Typeoneerror
    I've got a number of devices connected over wifi using GameKit. I have a simple UIAlertView popping up when peers receive data. All but the sendee show this alert view when data is sent, so I'm wondering if that's a bug in my app or if that's expected behavior. Should call a method manually at the same on the sendee device? For example, if I wanted to send a "GameStart" packet to the 4 phones, the peers would call startGame: in the receiveData:fromPeer:inSession:context: method when it receives that packet and the sendee would just sendData and call startGame: on itself. Does that sound right or is there a way to include the sendee in the sendData list so that it responds exactly the same as all connected peers?

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  • Reading PGP key information

    - by calccrypto
    can someone show a description of the information of what a pgp looks like if only the descriptions were there but not the actual information? something like (i dont remember if the values are correct): packet-type[4 bits], total length in bytes[16 bits], packet version type [4 bits], creation-time[32 bits], encryption-algorithm[8 bits], ...,etc,etc ive tried to understand rfc4880, but its tedious and confusing. so far, i am think i have extracted the 4 i wrote above, but i cant seem to get the rest of the information out. can anyone help? i know i can just find some pgp program, but the whole point of this is to allow me to learn how those programs work in the first place

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  • How can I get Syslogging to work on the JVM?

    - by Synesso
    I want to do syslogging from Java. There is a log4j appender, but it doesn't seem to work (for me anyway ... though Google results show many others with this issue still unresolved). I'm trying to debug the appender, so I've written the following script based upon RFC3164 It runs, but no logging appears in the syslog. // scala import java.io._ import java.net._ val ds = new DatagramSocket() val fullMsg = "<11>May 26 14:47:22 Hello World" val packet = new DatagramPacket(fullMsg.getBytes("UTF-8"), fullMsg.length, InetAddress.getLocalHost, 514) ds send packet ds.close I also tried using /bin/nc, but it doesn't work either. echo "<14>May 26 15:23:83 Hello world" > nc -u localhost 514 The Ubuntu command /usr/bin/logger does work, however. logger -p user.info hello world # logs: May 26 15:25:10 dsupport2 jem: hello world What could I be doing wrong?

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  • Object to Network serialization - with an existing protocol

    - by cpf
    I'm writing a client for a server program written in C++. As is not unusual, all the networking protocol is in a format where packets can be easily memcopied into/out of a C++ structure (1 byte packet code, then different arrangements per packet type). I could do the same thing in C#, but is there an easier way, especially considering lots of the data is fixed-length char arrays that I want to play with as strings? Or should I just suck it up and convert types as needed? I've looked at using the ISerializable interface, but it doesnt look as low level as is required.

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  • Weird Datagrid / paint behaviour

    - by Shane.C
    The scenario: A method sends out a broadcast packet, and returned packets that are validated are deemed okay to be added as a row in my datagrid (The returned packets are from devices i want to add into my program). So for each packet returned, containing information about a device, i create a new row. This is done by first sending packets out, creating rows and adding them to a list of rows that are to be added, and then after 5 seconds (In which case all packets would have returned by then) i add the rows. Here's a few snippets of code. Here for each returned packet, i create a row and add it to a list; DataRow row = DGSource.NewRow(); row["Name"] = deviceName; row["Model"] = deviceModel; row["Location"] = deviceLocation; row["IP"] = finishedIP; row["MAC"] = finishedMac; row["Subnet"] = finishedSubnet; row["Gateway"] = finishedGateway; rowsToAdd.Add(row); Then when the timer elapses; void timerToAddRows_Elapsed(object sender, System.Timers.ElapsedEventArgs e) { timerToAddRows.Enabled = false; try { int count = 0; foreach (DataRow rowToAdd in rowsToAdd) { DGSource.Rows.Add(rowToAdd); count++; } rowsToAdd.Clear(); DGAutoDevices.InvokeEx(f => DGAutoDevices.Refresh()); lblNumberFound.InvokeEx(f => lblNumberFound.Text = count + " new devices found."); } catch { } } So at this point, each row has been added, and i call the re paint, by doing refresh. (Note: i've also tried refreshing the form itself, no avail). However, when the datagrid shows the rows, the scroll bar / datagrid seems to have weird behavour..for example i can't highlight anything with clicks (It's set to full row selection), and the scroll bar looks like so; Calling refresh doesn't work, although if i resize the window even 1 pixel, or minimize and maximise, the problem is solved. Other things to note : The method that get's the packets and adds the rows to the list, and then from the list to the datagrid runs in it's own thread. Any ideas as to something i might be missing here?

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  • Raw socket implementation in windows?

    - by krishnakumar
    I need to create TCP/IP headers manually for my application. For that i used Raw socket. My system os is win xp (SP3). My code compiles fine :) but it throws a run time error: Initialising Winsock...Initialised successfully. Creating Raw TCP Socket...Raw TCP Socket Created successfully. Setting the socket in RAW mode...Successful. Enter hostname : 192.168.1.152 Resolving Hostname...Resolved. Enter Source IP : 192.168.1.151 Sending packet... Error sending Packet : 10022 I have set IP_HDRINCL to 1. What am i doing wrong? I switched off the firewall too but still get the same result.

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  • What's causing "Unable to retrieve native address from ByteBuffer object"?

    - by r0u1i
    As a very novice Java programmer, I probably should not mess with that kind of things. Unfortunately, I'm using a library which have a method that accepts a ByteBuffer object and throws when I try to use it: Exception in thread "main" java.lang.NullPointerException: Unable to retrieve native address from ByteBuffer object Is it because I'm not using a non-direct buffer? edit: There's not a lot of my code there. The library I'm using is jNetPcap, and I'm trying to dump a packet to file. My code takes an existing packet, and extract a ByteBuffer out of it: byte[] bytes = m_packet.getByteArray(0, m_packet.size()); ByteBuffer buffer = ByteBuffer.wrap(bytes); Then it calls on of the dump methods of jNetPcap that takes a ByteBuffer.

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