Is it possible to disconnect from one wi-fi network and connect to another network programatically using java?
My java application makes request to twitter using twitter4j. I can make only 350 requests per hour from a particular IP address. Now I'm sleeping for an hour before continuing my requests. But I have two Wi-Fi networks to connect to.
So when the limit exceeds and I get an exception, if I can switch between the networks, I can double the amount of work done. Is it possible in java?
It's only possible in java because java can call native code. You would need to implement this with native code in C or C++.
You could execute from your Java program an external program that would disconnect and reconnect (if you get an IP via DHCP).
Doesn't seem like the solution lies in the program, though. More in the way it's being used... or what it's being used (or shouldn't be used) for.
Related
I want to create Java Network servers which share one IP address. Something like the Piranha cluster:
Is there any solution similar to this?
P.S They have to work as a cluster. If one server is down the second one should handle the traffic.
Well the obvious solution would be to try to build your Java servers behind the Piranha layer; i.e. implement the application services on "real server 1", "real server 2", etcetera in Java
I'm pretty sure that you can't implement a Piranha-like solution in (pure) Java. The IP level load balancing is implemented in the network stack in the OS kernel (I think) of the "director". That rules out (pure) Java for two reasons:
It is impractical to put Java code inside the kernel.
To do it in user space in Java would entail using native code to read and write raw network packets. That is not possible in pure Java.
Besides, the chances are that you'd get better network throughput if the director layer was not implemented in Java, pure or otherwise.
Of course, there are other ways to do load balancing as well ...
Just create your standalone tcp/ip servers to listen on different ports (and ofcourse the IP address would be same as this is your requirement)
I have seen applications that can detect adjacent networks and desktops and devices attached to them. They can also know the computer/device name that is attached within 30 seconds.
Shall I try runtime.execute ping and net view command to do it, for I find them fast.
How can I capture the output as a result from these commands?
I tried sockets but they are time consuming.. only advantage, that I can also know that they have application installed (in which I created socket, enabling this communication).
Regards
Time-Outs in the initialization of Socket are useful, but you cannot have each connection connected within less than 300 Milli-seconds. On the server side also there is a timeout implementation. There is one sided communication in both. Multi-threading will help.
Can I create on Java monitoring program of network traffic? The program must control all network traffic which goes from computer program (including OS modules) to Network driver and back. If yes, How?
NOTE:
I want not only to monitor traffic also to control it. I want to implement such system on windows NT. It cannot be fulfilled o purely on Java. How can I perform it with the help of JNI?
Or maybe another variant. I am not acquaint with windows services, but still. I will write a program on C++ and register it as windows service. Then I call from my Java application this service (I don't know how to do this) and request network traffic. On the C++ program part all the traffic will be blocked if there is no Java program (or it doesn't request traffic); on the other way transmitted to this program. May be the java part can be implemented and work on an Java server (Glass Fish, JBoss). The C++ part in turn will transmit traffic to localhost.
What do you think about these ways?
When "monitoring of network traffic" then pcap, I'd say.
Googling "pcap java" brought me that as first hit: jNetPcap.
Did not test it, but pcap is the standard solution for native C programs. Cannot tell if the Java wrapper is good, but at least its website looks nice. ;-)
I need Java code to detect current connected devices to my network.
I tried the following idea :
- for all possible addresses check if this address is connected ( 254 loop )
- to speed up this process I created a thread for each check to make them run in parallel
Is there any way more efficient ??
Well there are lots of ways of detecting networked devices and you give no specifics on the nature of your situation.
The simplest (and most simplistic) approach I can think of would be to ping the broadcast address of your IP network and then consult the system's ARP table.
Unfortunately I have no particular strategy for accessing the ARP table from Java to suggest.
I'm thinking about writing a game which is based around a server, and several client programs connect to it. The game (very) basically consists of a list of items which a user can 'accept', which would remove it from the list on all connected computers (this needs to update very quickly).
I'm thinking about using a Java applet for the client since I would like this to be portable and run from a browser (mostly in Windows), as well as updating fast, and either a C++ or Java server running on Linux (currently just a home server, but possibly to go on a VPS).
A previous 'incarnation' of this game ran in a browser, and used PHP+mySQL for the backend, but this swamped the server quite a bit when several people connected (that was with about 8 people, this would eventually need to handle a lot more).
The users would probably all be in the same physical location (with the same public IP address), and the system would get several requests per second, all of which would require sending the list back to the clients.
Some computers may have firewall restrictions on them, so would you recommend using HTTP traffic, a custom port, or perhaps through SSH or some existing protocol?
Could anyone suggest some tips (threading, multiple requests of one item?), tools, databases (mySQL?), or APIs which would help me get started on this project? I would prefer C++ for the backend as it would be faster, but using Java would allow me to reuse code.
Thanks!
I wouldn't use C++ because of speed alone. It is highly unlikely that the difference in performance will make a real difference to your game. (Your network is likely to cloud any performance difference, unless you have 10 GigE between the client and server) I would use C++ or Java because you will get it working first using that language.
For anyone looking for a good networking API for c++ I always suggest Boost.Asio. It has the advantage of being platform independent, so you can compile a server for linux, windows etc. However, if you are not too familiar with c++ templates/boost the code can be a little overwhelming. Have a look, give it a try.
In terms of general advice. Given the description above, you seem to need a relatively simple server. I would suggest keeping it very basic, single threaded polling loop. Read a message from your connected clients (wait on multiple sockets), and respond appropriately. This eliminates any issue around multiple accesses to your list and other synchronization problems.
I might also suggest, before you re-write your initial incarnation. Try improving it, as you have stated:
and the system would get several requests per second, all of which would require sending the list back to the clients.
Given that each request removes an item from this list, why not just inform your uses which item is removed, rather than sending the entire list over the network time and time again? If this list is of any significant size, this minor change will result in a large improvement.