What is the difference between HTTP 100 and 200status code?
Are they the same?
I was told that 200 is the standard code when the HTTP request is successful without any errors whatsoever.
Is that right?
What about this 100 code? I have found different explanations on this status code. could somebody explain that using some real world example please?
Because right now I don't know the difference and both seem to be the same to me.
Let's me give you an example:
You’re sending a large object to the server using a PUT request, you may include a Expect header like this:
PUT /media/file.mp4 HTTP/1.1
Host: api.example.org
Content-Length: 1073741824
Expect: 100-continue
This tells the server that it should respond with a 100 Continue status code if the server is going to be able to accept the request:
HTTP/1.1 100 Continue
When the client receives this, it tells the client the server will accept the request, and it may start sending the request body.
The big benefit here is that if there’s a problem with the request, a server can immediately respond with an error before the client starts sending the request body.
A simple use-case is that a server might first require authentication using 401 Unauthorized, or it might know in advance that the Content-Type that the client wants to send to the server is not something the server will want to accept.
Mainly cited from :
https://evertpot.com/http/100-continue/
https://www.rfc-editor.org/rfc/rfc7231#section-5.1.1
From: http://www.rfc-editor.org/rfc/rfc7231.txt
6.2.1. 100 Continue
The 100 (Continue) status code indicates that the initial part of a
request has been received and has not yet been rejected by the
server. The server intends to send a final response after the
request has been fully received and acted upon.
When the request contains an Expect header field that includes a
100-continue expectation, the 100 response indicates that the server
wishes to receive the request payload body, as described in
Section 5.1.1. The client ought to continue sending the request and
discard the 100 response.
If the request did not contain an Expect header field containing the
100-continue expectation, the client can simply discard this interim
response.
(edited, thank you Julian for noticing :)
Related
I was just reading this Wikipedia article on HTTP pipelining and from the diagram it appears that responses can be sent concurrently on one connection. Am I misinterpreting the diagram or is this allowed?
Section 8.1.2.2 of RFC 2616 states:
A server MUST send its responses to those requests in the same order
that the requests were received.
Whilst that stops short of explicitly ruling out concurrent responses, it does not mention a need to ensure that responses must not only start in the correct order with relation to requests, but also finish in the correct order.
I also cannot imagine the practicalities of dealing with concurrent responses - how would the client know to which response the received data applies?
Therefore my interpretation of the RFC is that whilst additional requests can be made whilst the response to the first request is being processed, it is not allowedfor the client to send concurrent requests or the server to send concurrent responses on the same connection.
Is this correct? I've attached a diagram below to illustrate my interpretation.
It would prevent the problems I mentioned from occurring, but it does not appear to completely align with the diagram in Wikipedia.
Short answer: Yes, clients and servers can send requests and responses concurrently.
However, a server cannot send multiple responses to one request, i.e. the request response pattern still applies. RFC 2616 (and the Wikipedia article you are refering to) simply state that a client does not need to wait for the server's response to send an additional request on the same connection. So the requests in your diagram look good :).
But the server doesn't have to wait for each of its responses to finish before it can start transmission of the next response. It can just send the responses to the client as it receives the client's requests. (Which results in the diagram shown in the Wikipedia article.)
How does the client know to which request a response applies?
Well, let's ignore that whole network delay stuff for a minute here and assume that pipelined request or response messages arrive at once but only after all of them have been sent.
The client sends its requests in a certain order (without waiting for responses inbetween requests).
The server receives the requests in the same order (TCP guarantees that) all at once.
The server takes the first request message, processes it, and stores the response in a queue.
The server takes the second request message, processes it, and stores the response in a queue.
(You get the idea...)
The server sends the contents of that queue to the client. The responses are stored in order so the response to the first request is at the beginning of that queue followed by the response to the second request and so on...
The client receives the responses in the same order (TCP guarantees that) and associates the first response with the first request it made and so on.
This still works even if we don't assume that we receive all the messages at once because TCP guarantees that the data that was sent is received in the same order.
We could also ignore the network completely and just look at the messages that are transferred between server and client.
Client -> Server
GET /request1.html HTTP/1.1
Host: example.com
...
GET /request2.html HTTP/1.1
Host: example.com
...
GET /request3.html HTTP/1.1
Host: example.com
...
Server -> Client
HTTP/1.1 200 OK
Content-Length: 234
...
HTTP/1.1 200 OK
Content-Length: 123
...
HTTP/1.1 200 OK
Content-Length: 345
...
The great thing about TCP is that this particular stream of messages always looks the same. You can send all of the requests first and then receive the responses; you can send request 1 first, receive the first response, send the remaining requests, and receive the remaining responses; you can send the first and part of the second request, receive part of the first response, send the remaining requests, receive the remaining responses; etc. Because TCP guarantees to keep the order of the transmitted messages, we can always associate the first request with the first response and so on.
I hope this answers your question...
I am qurious if there is any standard method in HTTP 1.X protocol to tell there is a problem on the server during http response that started as 200 OK.
How to tell there's any error on the server if 200 OK header is already returned and we are currently sending the response body? In some standards-compilliant way.
UPD : There is a duplicate, but without a single answer (!) HTTP: error during reply after 200 OK status code.
To be specific: I can not use Content-Length for checking at response end, because the length can't be known at response start.
Additionaly, I can't cache the whole response on the server before sending (because it is too big and I will run out of memory, and it's too long to generate so the user can't wait, etc...).
There is no standard method to do what you want.
To be precise, the standard method is to buffer the response on the server, then send a 200 OK and the Content-Length, followed by the content. As stated, this does not work for you.
The only alternative I can think of, is to wrap the content in some format that makes it discoverable whether it was sent correctly. For example, you might end it with a hash or even a digital signature. But obviously, such mechanisms are not part of the HTTP standard.
All,
My requirement is fairly simple. I have to perform a simple HTTP POST to an IP:port combination. I used simple socket programming to do that and I have been successful in sending across my request to them and also get back response from them. The only problem being that the response is always a HTTP 400: Bad Request followed by my HTTP POST message. I am not sure if the problem is with the client or the server. My only guess being that there might be a problem with my data that I am sending. This is what my POST looks like
POST /<Server Tag> HTTP/5.1
Content-Length: xxx
--Content--
and the response from the server looks something like this
HTTP/1.1 400 Bad Request
Content-Length: xxx
--Same content that I sent them--
I was not sure If I could put in the IP of the server here so kept myself to using . I am pretty sure that the problem would not be there since I get back some response from the server and confident about the connection. Can someone help me ?
PS: Some pointers about my POST:
1) HTTP 5.1 was requested by the server and I am not sure if that is correct
2) I have played around with the number of line spaces after the content length. I have tried giving one and two lines. Not sure if that would make a difference. On wireshark though I see a difference with the number of line spaces as with a single line space the protocol is specified as TCP but with two it changes to HTTP. The response is always received on HTTP protocol. Some explanation on the difference would also help
Thanks
edit: the other thing that confuses me is that the response has a HTTP 1.1 and not a 5.1 that I had sent. I have also tried changing my post to 1.1 with no success
edit2: Based on suggestion form fvu and others, I used WebClient to Upload my request. Still got back a 400. The header that was generated by the WebClient looks like this
POST <server tag> HTTP/1.1
Host: <IP:PORT>
Content-Length: 484
Expect: 100-continue
Connection: Keep-Alive
The issue I see with this might be that the server was not expecting all the details in the header. The server has requested only the Content-Length from us. Would that be a problem?
Thanks
You can use a debugging proxy to view a client request and a server response to figure out what your client socket program needs to do.
But first you need to create a simple web page that a browser displays, allows you to do a POST from the browser to the web server, and get a simple response back from the server.
HTTP/5.1 is either wrong or misused by the programmer of the server application
You should get a valid example from the server api to check your protocol implementation first.
I saw Expect: 100-continue in some PUT request(uploading a file), what does it mean?
What is supposed to happen, is you're supposed to send the request headers with an:
Expect: 100-continue
header. Then, after you have sent the headers, but before you send the payload, you should check to see if you get the 100 response, or a 417 response. If you get the 100 response, you can continue sending the payload. If you don't, you should stop.
The premise is that when you're getting ready to send that 10GB file, this gives the server an opportunity to say "Hold on, cowboy" and then you can handle the process more elegantly than the server simply slamming the socket shut on you.
The fact that you got a 100 back, and you weren't expecting it, says you probably got both the 100 and the 200 (or whatever) response. The 100 was sent to you after the headers were sent, then the final response when the request was finished.
That you weren't paying attention to it is really a detail.
But, ideally, in the future your processing can consider the proper mid-request response.
If you did NOT send the Expect header, the server should not have sent you the 100, since you weren't telling it that you were going to process it. If you DID send the Expect header, then the 100 should not have come as a surprise.
I have an HTTP server that returns large bodies in response to POST requests (it is a SOAP server). These bodies are "streamed" via chunking. If I encounter an error midway through streaming the response how can I report that error to the client and still keep the connection open? The implementation uses a proprietary HTTP/SOAP stack so I am interested in answers at the HTTP protocol level.
Once the server has sent the status line (the very first line of the response) to the client, you can't change the status code of the response anymore. Many servers delay sending the response by buffering it internally until the buffer is full. While the buffer is filling up, you can still change your mind about the response.
If your client has access to the response headers, you could use the fact that chunked encoding allows the server to add a trailer with headers after the chunked-encoded body. So, your server, having encountered the error, could gracefully stop sending the body, and then send a trailer that sets some header to some value. Your client would then interpret the presence of this header as a sign that an error happened.
Also keep in mind that chunked responses can contain "footers" which are just like HTTP headers. After failing, you can send a footer such as:
X-RealStatus: 500 Some bad stuff happened
Or if you succeed:
X-RealStatus: 200 OK
you can change the status code as long as response.iscommitted() returns false.
(fot HttpServletResponse in java, im sure there exists an equivalent in other languages)