These are all just from the standard library. This lets me easily extract different parts of the url like its protocol, hostname, port, etc. A socket is an object through which network communication can happen.
In order to send a message through a socket, it must be in the form of a buffer, not a string or number. The first argument is the message as a buffer. Finally the last argument is a callback for when the message has finished sending. Here we tell the socket how to handle incoming messages. Whenever a message comes back through the socket it will be passed to the callback function.
Now we know how to send and receive messages through UDP, but in order to get a list of peers from the tracker, the tracker will be expecting messages to follow a specific protocol. In short you must:. Since the amount of code related to the tracker is starting to get large, at this point I want to create a new file called tracker. When we finally get the list of peers we pass it to the callback.
The other 6 functions are as follows:. Since both responses come through the same socket, we want a way to distinguish them. Each message is a buffer with a specific format described in the BEP. This tells us that our message should start out with a bit i. Since we just write 8 bytes, the index of the next part is 8. Now we write bit integer 4 bytes with the value 0. This moves us up to an offset of 12 bytes, and we write a random bit integer.
First we require the built-in crypto module to help us create a random number for our buffer. Then we create a new empty buffer with a size of 16 bytes since we already know that the entire message should be 16 bytes long. Here we write the the connection id, which should always be 0x when writing the connection request.
We use the method writeUInt32BE which writes an unsigned bit integer in big-endian format more info here. We pass the number 0x and an offset value of 0.
And then again the number 0x at an offset of 4 bytes. The 0x indicates that the number is a hexadecimal number, which can be a more conventient representation when working with bytes. The reason we have to write in 4 byte chunks, is that there is no method to write a 64 bit integer. Actually node. Next we write 0 for the action into the next 4 bytes, setting the offset at 8 bytes since just wrote an 8 byte integer. This values should always be 0 for the connection request.
For the final 4 bytes we generate a random 4-byte buffer using crypto. To copy that buffer into our original buffer we use the copy method passing in the offset we would like to start writing at. You can see I read the action and the transaction id as unsigned 32 bit big-endian integers, passing in the offset.
Then I just use the slice method to get the last 8 bytes. Many of the concepts here are the same as the connect request and response. I created a new file called util. A peer id can basically be any random byte string but most clients follow a convention detailed here. As you can see the id is only generated once. Notice that this function takes a torrent parameter now. Because the number is negative you cannot used the unsigned version.
The addresses come in groups of 6 bytes, the first 4 represent the IP address and the next 2 represent the port. So our code will need to correctly break up the addresses part of the response. Most of this code is pretty straightforward. Also a bit surprising that you can call join on a buffer. This is a bit fancy as it coerces the bytes into a string but seems to work and I think it looks nice.
I created a new file called torrent-parser. This means I also want to move the code for opening a torrent file here. Remember it looked something like this:. Last time we pulled the announce property from this object. Can you see that it also has an info property? If you were take the info property and pass it through a SHA1 hashing function, you would get the info hash!
You can apply a SHA1 hash easily using the built-in crypto module. Why use a SHA1 hashing function? A hashing function returns a fixed length buffer in this case bytes long.
Actually we just send the whole size of the torrent files. There are two cases we have to consider - torrents that have one file or more than one file. But if it has multiple files, it will have a torrent. We have to iterate over these file objects and sum their length property. The easiest way to deal with this is to install a module to handle larger number for us. Install it with the command:. You can see that I write the number into a buffer using the bignum. This is also the buffer size required by the announce request.
Now almost all the pieces have come together for communicating with the tracker. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. How to write a simple Bittorrent application? Ask Question. Asked 10 years, 10 months ago. Active 11 months ago. Viewed 44k times. How to test an application if all you have is one laptop. Improve this question. It's at the top of the qBitTorrent window Windows or the screen Mac. A drop-down menu will appear. Click Torrent Creator.
You'll see this in the drop-down menu. Doing so opens the Torrent Creator window. Click Select file. It's near the top of the page. A pop-up window will appear. If you want to create a torrent using an entire folder, click Select folder here instead. Select the file you want to use. Go to the folder location of the file or folder you want to use, click once the file or folder, and click Open or Choose.
Check the "Start seeding immediately" box. This will ensure that you are uploading the torrent's files, meaning that someone else will be able to download them. Failing to seed your torrent's files will result in a dead torrent. Enter your copied tracker URLs. Many of the trackers in this list won't work, which is why you're copying and pasting all of them into the URL text box instead of just selecting one.
Click Create Torrent. It's at the bottom of the window. Select a save location. Click the folder in which you want to save your created torrent file. Click Save. Doing so will save your file and begin seeding the torrent, meaning that the torrent is now available for download. Send the torrent to a friend. For someone to download your torrent's files, they'll just need to double-click the torrent to open it in their default torrent application and then confirm the torrent's files' download location.
As long as you're seeding the torrent, your friend should be able to download the torrent with no trouble. Did you know you can get expert answers for this article? Unlock expert answers by supporting wikiHow. Luigi Oppido. Support wikiHow by unlocking this expert answer. Yes No. Not Helpful 4 Helpful 2. This has been going on for days and no matter what I do, I cannot seem to find a fix! Please help! AUser I have also been having this issue, any resolution yet? Hovsep A can you drag and drop the uTorrent file to uTorrent window?
Rajaa C Select look for an app in the store.
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