I'm working on an HTTP parser and was wondering how can i parse traffic that is sent with no content length and no EOF?
Read the data until the connection is shutdown (from the other side).
This is how the original HTTP worked, but it's not very nice; if the server crashes, or you lose network connectivity in the middle of the transmission, you might not notice that the response is truncated.
Related
When an image is uploaded from the client's machine to the client (browser), it requires FileReader() API in html, thereafter a base64 encoded url (say) of the image is sent in chunks to the server, where it needs to be re-assembled. All of this is taken care by the developer.
However, when an image is sent from the server to the client, only the directory path of the image inside the server machine suffices, no chunking and encoding is required.
My questions are:
1. Does the server send the image in chunks to the html file. If it does not, how does sending full images not bottle server's network? What would happen in case of large video files?
2. In what form of binary data is the image sent to the client - base64url / ArrayBuffer / binarystring / text / etc.
3. If the server does send the image in chunks, who is doing the chunking and the re-assembly on the client thereafter?
Thanks.
HTML isn't really important here. What you care about are the transport protocols used - HTTP and TCP, most likely.
HTTP isn't chunked by default, though there are advanced headers that do allow that - those are mostly used to support seeking in large files (e.g. PDF, video). Technically, this isn't really chunking - it's just the infrastructure for allowing for partial downloads (i.e. "Give me data from byte 1024 to byte 2048.").
TCP is a stream-based protocol. From programmer point of view, that's all there is to it - no chunking. Technically, though, it will process your input data and send it as distinct packets that are reassembled in-order on the other side. This is a matter of practicality - it allows you to manage data latency, streaming, packet retransmission etc. TCP handles the specifics during connection negotiation - flow control, window sizing, congestion control...
That's not the end of it, though. All the other layers add their own bits - their own ways to package the payload and split it as necessary, their own ways to handle routing and filtering, their own ways to handle congestion...
Finally, just like HTTP natively supports downloads, it supports uploading data as well. Just send an HTTP request (usually POST or PUT) and write data in a format the server understands - anything from text through base-64 to raw binary data. The limiting factor in your case isn't the server, the browser or HTTP - it's JavaScript. The basic mechanism is still the same - a request followed by a response.
Now, to address your questions:
Server doesn't send images to the HTML file. HTML only contains an URL of the image[1], and when the browser sees an URL in the img tag, it will initiate a new, separate request just for the image data. It isn't fundamentally different from downloading a file from a link. As for the transfer itself, it follows pretty much exactly the same way as the original HTML document - HTTP headers, then the payload.
Usually, raw binary data. HTTP is a text-based protocol, but it's payload can be arbitrary. There's little reason to use Base-64 to transfer image data (though in the past, there have been HTTP and FTP servers that didn't support binary at all, so you had to use something like Base-64).
The HTTP server doesn't care (with the exception of "partial downloads" mentioned above). The underlying network protocols handle this.
[1] Nowadays, there's methods to embed images directly in the HTML text, but it's of varying practicality depending on the image size, caching requirements etc.
I am looking for a way to dump http request & reaponse body (json format) in resteasy on wildfly 8.2.
I've checked this answer Dump HTTP requests in WildFly 8 but it just dumps headers.
I want to see the incoming json message and outgoing one as well.
Can configuration do it without filter or any coding?
Logging HTTP bodies is not something frequently done. That's probably the primary reason for RequestDumpingHandler in Undertow only logging the header values. Also keep in mind that the request body is not always very interesting to log. Think for example of using WebSockets or transmitting big files. You can write your own MessageBodyReader/Writer for JAX-RS, and write to a ByteArrayOutputStream first, then log the captured content before passing it on. However, given the proven infeasibility of this in production, I think your mostly interested in how to do this during development.
You can capture HTTP traffic (and in fact any network traffic) using tcpflow or Wireshark. Sometimes people use tools such as netcat to quickly write traffic to a file. You can use for example the Chrome debugger to read HTTP requests/responses (with their contents).
I am working on a TCP-based proxy that must first do a REQ/REPLY handshake in json on a given connection. Because JSON is a self-delimiting protocol I reach for Go's json.Decoder to pull off this work which does the job nicely.
Here are the steps I take:
Dial a connection to a remote server
Write a single json request to a remote server (REQ)
Read a single json reply from the same remote server (completing the proxy handshake REPLY)
Upon a valid json handshake, pass the client connection onto another part of the code which will (going forward) switch to a text based protocol from this point on.
The problem is, when json.Decoder reads data into its internal buffer it can potentially read more data than it needs in which case the json.Decoder has a Buffered() method which gives back an io.Reader with the remainder of the data.
This data (available in the Buffered() method) is now the text-based protocol data which needs to get read from the connection after the json hand-shake did its work. But if I pass the connection forward as is without considering the left over buffer, the connection gets into a locked state because it is waiting to read this data which never comes. The code that deals with the text-based protocol expects a net.Conn going forward and once I pass the connection forward (after the json handshake has been made) the code utilizing the connection understands how to speak the text-based protocol at this point on. So there should be a clear boundary of work.
My question is what is the ideal way to solve this issue so I can still take advantage of the json.Decoder, but ensure that when I pass the connection to a different part of the code in my proxy I know the start of the data for the text-based protocol will still be readable. I somehow need to take the remaining data in the json.Decoder's Buffered() method and put that back in front of the connection so it can be properly read going forward.
Any insight is much appreciated.
You can try
type ConnWithBuffIncluded struct{ //Implement net.Conn so can be passed through pipeline
net.Conn
json.Decoder
}
func (x ConnWithBuffIncluded) Read(p []byte) (n int, err error){ //Will Read both sources
return io.MultiReader(x.Decoder.Buffered(), x.Conn).Read(p)
}
How do you know if a socket server or web server is done transmitting a HTTP GET request when using ProgressEvent.SOCKET_DATA ?
I doing my socket request with socket.writeUTFBytes('GET /index.php HTTP/1.1\r\n');
But the 'answer' is so big that i get multiple ProgressEvent.SOCKET_DATA. How do i know how much data it is supposed to transmit to me ? Or when it's done transmitting ?? Or even how many progressEvents i will get out of this request ? So far I'm using a timer that checks if the server is still transmitting but this isn't a very clean way of doing things..
How do i know how much data it is supposed to transmit to me? Or when it's done transmitting ??
By reading the Content-length header if that is sent by the server, or by waiting until the server closes the connection, or by reading until you've encountered a last-chunk (0<CRLF><CRLF>) if chunked transfer encoding is enabled, or any of the other indications that a full response has been received.
For simplicity, use a HTTPService or if that doesn't fit your needs, use a library that implements an HTTP client.
Or even how many progressEvents i will get out of this request ?
There is no way to tell.
When an "onmessage" event fires in the web socket protocol are you guaranteed the full message or is it more like a straight TCP connection where you buffer the data first and then try to extract packets.
There is protocol level support for fragmented messages and streaming. But this behavior is not represented in the current Javascript API, (reference). So yes, if you receive a message, it is indeed an entire message even if it was sent as many fragments.