How to change tcp information in layer 3 in java ?(ip spoofing) how to change layer 2 information ? is there any good library for it in java ? it need raw socket?
JpCap may be what you want http://netresearch.ics.uci.edu/kfujii/Jpcap/doc/
unfortunately to need access to the TCP/IP packet structures you need to work at very low level (you need the kernel headers in Linux for instance) so yes, you will definitely 100% need to do this outside java in a native library and call the code in your Java app.
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I want to add bandwidth measurements to my servers (written in pure java). I am thinking of an API that look like
MeasureBandwidthSignletone.getInstance().startMeasuring();
......
.....//here I may connect to a db or using http (HttpUrlConnection)...
.....
MeasureBandwidthSignletone.getInstance().endMeasuring();
Problem is that I have many different kinds of code that access the network (jdbc, HttpUrlConnection, FTP, etc...) I was wondering if I can somehow attach a threadlocal monitor to sockets, which will allow me to know how many bytes were uploaded or download.
I know one way would be using ASM / AspectJ to change the byte code - but is there any simpler way to plug in to the java socket API?
Thank you
What about setting a custom made SocketFactoryImpl? Can that work?
That could also work for a specific version of the JVM. If you know which version you are targeting you could create a modified version of this class.
The reason this won't work for a generic JVM is this class uses internal APIs which can be different between versions which is why byte code injection is more likely to work for a broad range of JVMs.
I'd like to somehow get control over active sockets on my computer with java/scala. For example, if a program has stablished a tcp connection, i want to be able to retrieve and listen/write onto this socket.
So, the first question is: is that possible?
And the second: how?
You can do this by writing a custom Socket factory. This is fairly complicated and I don't suggest you do this unless you are trying a to hack a program you have no control over (again a very bad idea)
Instead I suggest you monitor your own usage. When you read/write from a Socket you also keep any information you need. i.e Its your program so change it to do what you need.
I found a java wrapper of lipcap http://jnetpcap.com/ that let me do the sort of things i was after. From the web:
jNetPcap is an open-source java library. It contains:
A Java wrapper for nearly all libpcap library native calls
Decodes captured packets in real-time
Provides a large library of network protocols (core protocols)
Users can easily add their own protocol definitions using java SDK
jNetPcap uses a mixture of native and java implementation for optimum packet decoding performance
I need to transfer files fast over the Internet from a Java server to C++ clients, where often many clients would need the same files. I was looking at say transferTo() in Java which sounds like it would be a decently optimized function to send files. However, I'm not sure when I use transferTo() how to best receive that in C++ (i.e. is it just a raw data transfer, how do I determine when the file is over on the client side, etc.). I need this to work on both Windows and Linux. Also, other than transferTo(), would there be some way to be more efficient, especially by taking advantage of the fact that many clients will usually need the same files? I'm not sure how to do say multicast etc. Also, I'm using application-level security rather than a VPN, and on the Java server, encrypting with AES and using MAC digital signing, so I'm also looking for a cross-platform library recommendation to deal with the crypto on the C++ side with minimal pain.
I'm very proficient in C++ but have no previous experience with network programming, so please consider than in any suggestions.
Thanks.
An embedded webserver? http-transfers are efficient enough for you?
The simplest embeddable Java webserver I remember seeing is http://acme.com/java/software/Acme.Serve.Serve.html. We use embedded Jetty 6 in production at work, but that takes more elbow grease.
If your clients doesn't know where to find your webserver in the first place, consider announcing using Zeroconf. http://jmdns.sourceforge.net/
For scalability reasons, Thorbjørns suggestion of using http seems like a very good idea as it would allow you to easily set up http proxies for caching, use standard load balancing tools and so forth.
If you are looking to transfer more than just a blob of data, you might want to have a look at googles protocol buffers. They allow for very easy and fast encoding/decoding on the java and c++ end.
Consider chunking the file and sending via UDP datagram. C++ can re-compile as it receives it. Have you considered implementing/embedding an existing P2P protocol implementation?
If you need effecient transfer to many clients then your bottleneck is the server.
For this please look at the bit-torrent protocol as it distributes the transfer between the clients.
I know that the Java can use the Socket Programming to send an Object. Apart from socket programming, anything other way to do it?
Java's Remote Method Invocation (RMI) is probably the easiest and most widely supported way.
Java's Advanced Socket Programming describes marshalling objects over a socket.
Control a high-speed robot hand to type it in.
Pretty well every other thing you can do will be a layer built on sockets.
RFC1149!
Attach rubber band to computer A
Put Object in rubber band.
Pull back, aim at Computer B.
Let go.
Via web service for example. But its build on top on sockets again.
SOAP (Simple Object Access Protocol).
Serialize the object, write to a file, copy the file if the computers are network connected if not use a removable disk and deserialize it.
Objects can be transferred via a shared database.
I work near a production system that's been doing this for 10 years.
Ironically, except in rare cases, DB connections are also implemented via sockets.
No. Sockets are how computers communicate. Other than writing the data to some media and physically transporting it between computers, you will have to use sockets.
At the lowest level, data is transferred over sockets as bytes. So first you need to serialize your object to bytes, then you can send it, then on the other side you need to deserialize the object from the bytes.
Approaching your question less literally, there are Java libraries that handle the serialization automatically and hide the nastiness of dealing directly with sockets. I recommend KryoNet. KryoNet can do remote method invocations, and a lot simpler and more efficiently than Java's built-in RMI support.
What would be the easiest way to be able to send and receive raw network packets. Do I have to write my own JNI wrapping of some c API, and in that case what API am I looking for?
EDIT: I want to be able to do what wireshark does, i.e. record all incomming packets on an interface, and in addition be able to send back my own created packets. And I want to do it on a mac.
If you start with the idea that you need something like a packet sniffer, you'll want to look at http://netresearch.ics.uci.edu/kfujii/jpcap/doc/.
My best bet so far seems to be the BPF api and to write a thin JNI wrapper
Raw Socket for Java is a request for JDK for a looong long time. See the request here. There's a long discussion there where you can look for workarounds and solutions. I once needed this for a simple PING operation, but I can't remember how I resolved this. Sorry :)
You can't access raw sockets from pure Java, so you will need some sort of layer between your Java code and the network interfaces.
Also note that access to raw sockets is normally only available to "root" processes, since otherwise any user could both a) sniff all traffic, and b) generate spoofed packets.
Rather than write your whole program so that it needs to run as "root", you might consider having the packet capture and generation done in a standalone program with some sort of IPC (RMI, named pipe, TCP socket, etc) to exchange the data with your Java app.
TINI is a java ethernet controller, which may have libraries and classes for directly accessing data from ethernet frames to TCP streams. You may be able to find something in there that implements your needed classes. If not, there should be pointers or user groups that will give you a head start.