I'm writing an application that needs to send data to a socket and receive data from the socket.
I know how to do this; I've done it several times before it other apps.
Unfortunately, the only documentation I have for the server I need to communicate with in the current project is in the form of a JavaScript file that uses some library called "Socket.IO". I am not familiar with this library (or JavaScript for that matter).
The JavaScript code contains statements such as "io.connect" with a parameter that looks like a web site URL, as well as multiple "emit" statements that have at least two parameters each. I need to know exactly what these statements are doing in terms of: what host and port is it connecting to? What bytes is it sending to the socket?
Where can I find this information?
Thanks,
Frank
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I want to write a Forth program for my Raspberry Pi. This program shall read some sensor data from an existing file and send it to a website where the data gets stored.
Searching the web there was plenty of documentation about how easy and fast Forth is and how to calculate Fibonacci numbers. But how can I request a URL? How can I send data to a website and process the result?
If there's no socket support: is it possible to start an external program like curl/wget to do the request?
It is not obvious from the question what the Forth implementation is used.
For example, Gforth (that is available on Raspberry Pi)
has some support of the sockets and also it allows to start an external program using system word. See my answer on the similar question: How do I read raw code from a website in Gforth?
Example of creating curl child process in Gforth:
S" curl https://example.com/" system
In any case,
it seems that the most promising approach for the given problem is to develop a binding to libcurl (if it doesn't exist yet for the used Forth implementation).
I need to stream data from a web server to clients. The data is location data that is collected and stored on the server. The clients will click a button on an html page to 'opt in' to start receiving the data. This data is never ending and there is at least one of the clients that needs to receive the data 24-7, with as few breaks as possible. The data being streamed will be client specific, as each client wont receive the exact same data.
I've done several multi-threaded tcp servers over sockets, and websockets are the way I would like to attack this, but the requirements are that this has to work in ie9.
The initial requirement was that this be a vb.net cgi executable - but during testing, I havent been able to 'use' the stream from the vb.net executable until the app finishes - like it wasn't able to flush the stdout even though I was specificly using the console.out.flush(). So If this isn't a viable option, and I can support this with facts, then I can get this requirement changed.
I've also read quite a bit about using a third party server to stream the data like Orbit and APE I think was a couple of them, but requirements are for 1 server - the web server. No other hardware can be required.
I'm pretty sure the vb.net CGI isn't the ideal solution based on what i've found, but is it doable or do I need to abandon that solution and move on to a newer technology , ISAPI? Any ideas or suggestions, even if they just point me in the right direction, are greatly appreciated.
You might go few ways.
If you would go C# .Net, then you might look into Silverlight solution. But it requires plugin in browser to be installed (like Flash). Good thing here, is that you are able to send data through normal sockets, in pure realtime from server. In same time Silverlight uses .Net so it makes some code to be shared. That helps development process. As well the way it will work in different browsers will be same.
You might have a look in similar solution using Java Applet with Java backend (can be even .Net, but again, easier to develop when both in same language).
Another option is to have fron-end using WebSockets, but as you know its not supported in IE9 and below (IE10 promises to be), and Opera is not supporting it as well.
Backend can be done in what you prefer. But bear in mind that WebSockets uses framing, and for constant but little packets its not efficient, because if you send 10 bytes, then it will create frame 2-12 bytes, and TCP packet header that is 40 bytes in average.
To support older browsers you might have a look in long-polling, but it is not as reliable as websockets.
As well it is important to calculate the amount of data and approximate amount of users that will use your system. Based on calculations you will have approximate information about how real it is, and what server will be required to handle.
I am trying to build an application that can inform a user about website specific information whenever they are visiting a website that is present in my database. This must be done in a browser independent way so the user will always see the information when visiting a website (no matter what browser or other tool he or she is using to visit the website).
My first (partially successful) approach was by looking at the data packets using the System.Net.Sockets.Socket class etc. Unfortunately I discoverd that this approach only works when the user has administrator rights. And of course, that is not what I want. My goal is that the user can install one relatively simple program that can be used right away.
After this I went looking for alternatives and found a lot about WinPcap and some of it's .NET wrappers (did I tell you I am programming c# .NET already?). But with WinPcap I found out that this must be installed on the user's pc and there is nog way to just reference some dll files and code away. I already looked at including WinPcap as a prerequisite in my installer but that is also to cumbersome.
Well, long story short. I want to know in my application what website my user is visiting at the moment it is happening. I think it must be done by looking at the data packets of the network but can't find a good solution for this. My application is build in C# .NET (4.0).
You could use Fiddler to monitor Internet traffic.
It is
a Web Debugging Proxy which logs all HTTP(S) traffic between your computer and the Internet. Fiddler allows you to inspect traffic, set breakpoints, and "fiddle" with incoming or outgoing data. Fiddler includes a powerful event-based scripting subsystem, and can be extended using any .NET language.
It's scriptable and can be readily used from .NET.
One simple idea: Instead of monitoring the traffic directly, what about installing a browser extension that sends you the current url of the page. Then you can check if that url is in your database and optionally show the user a message using the browser extension.
This is how extensions like Invisible Hand work... It scans the current page and sends relevant data back to the server for processing. If it finds anything, it uses the browser extension framework to communicate those results back to the user. (Using an alert, or a bar across the top of the window, etc.)
for a good start, wireshark will do what you want.
you can specify a filter to isolate and view http streams.
best part is wireshark is open source, and built opon another program api, winpcap which is open source.
I'm guessing this is what you want.
capture network data off the wire
view the tcp traffic of a computer, isolate and save(in part or in hole) http data.
store information about the http connections
number 1 there is easy, you can google for a winpcap tutorial, or just use some of their sample programs to capture the data.
I recomend you study up on the pcap file format, everything with winpcap uses this basic format and its structers.
now you have to learn how to take a tcp stream and turn it into a solid data stream without curoption, or disorginized parts. (sorry for the spelling)
again, a very good example can be found in the wireshark source code.
then with your data stream, you can simple read the http format, and html data, or what ever your dealing with.
Hope that helps
If the user is cooperating, you could have them set their browser(s) to use a proxy service you provide. This would intercept all web traffic, do whatever you want with it (look up in your database, notify the user, etc), and then pass it on to the original location. Run the proxy on the local system, or on a remote system if that fits your case better.
If the user is not cooperating, or you don't want to make them change their browser settings, you could use one of the packet sniffing solutions, such as fiddler.
A simple stright forward way is to change the comupter DNS to point to your application.
this will cause all DNS traffic to pass though your app which can be sniffed and then redirected to the real DNS server.
it will also save you the hussel of filtering out emule/torrent traffic as it normally work with pure IP address (which also might be a problem as it can be circumvented by using IP address to browse).
-How to change windows DNS Servers
-DNS resolver
Another simple way is to configure (programmaticly) the browsers proxy to pass through your server this will make your life easier but will be more obvious to users.
How to create a simple proxy in C#?
How do they do this? I would like to have web pages with data fields that change in real time as a person views the web page. Here is an example.
How do they do this? JQuery? PHP?
I need to connect my field data to mySQL database.
There are two approaches:
Polling
Client requests data on a regular basis. Uses network and server resources even when there is no data. Data is not quite 'live'. Extremely easy to implement, but not scalable.
Push
Server sends data to the client, so client can simply wait for it to arrive instead of checking regularly.
This can be achieved with a socket connection (since you are talking about web pages, this doesn't really apply unless you are using Flash, since support for sockets in the browser in the browser is currently immature) - or by using the technique known as 'comet'.
Neither socket connections nor comet are particularly scalable if the server end is implemented naively.
- To do live data on a large scale (without buying a boat load of hardware) you will need server software that does not use a thread for each client.
I did it with JavaScript timer set execution in milliseconds, each time timer executed function that queried Server with Ajax and returned value(possibly JSON format), then you you update your field with the value. I did it each 5 sec and it works perfectly. In ASP.NET I think it called Ajax Timer Control.
There are two things needed to do this:
Code that runs on the browser to fetch the latest data. This could be Javascript or something running in a plugin such as Silverlight or Flash. This will need to periodically request updated content from the server.
Which leads to a need for...
Code that runs on the server to retrieve and return the latest data (from the database). This could be created with any server sided scripting language.
We need is to push sports data to a number of different client types such as ajax/javascript, flash, .NET and Mac/iPhone. Data updates need to only be near-real time with delays of several seconds being acceptable.
How to best accomplish this?
The best solution (if we're talking .NET) seem to be to use WCF and streaming http. The client makes the first http connection to the server at port 80, the connection is then kept open with a streaming response that never ends. (And if it does it reconnects).
Here's a sample that demonstrates this: Streaming XML.
The solution to pushing through firewalls: Keeping connections open in IIS
I would go with XML. XML is widely supported on all platforms and has lots of libraries and tools available for it. And since it's text, there are no issues when you pass it between platforms.
I know JSON is another alternative, but I'm not familiar enough with it to know whether or not to recommend it in this case.