I ran wireshark for a while and opened a few webpages now my class assignment is asking me to find out the number of http and https connections established. Can you suggest commands or filters to find these out?
HTTP is connection-less, that means client and server knows about each other during current request and response only. You can open the .pcapng file and then
Click on “Statistics”
Select “HTTP”
Select “Packet Counter“
In my case, I can 14 requests and 14 responses. (Success 2xx).
Related
We are facing 499 error when we close the browser tab before getting response for the request. We are using nginx in k8s.
I have tried by configuring "proxy_ignore_client_abort: on" property in ingress configuration, still we are getting issue even after configuring the above property. Please suggest me way to fix this issue.
Firstly we are supposed to know that the nginx throw 499 if the client actively disconnected the connection. So it you may not pay much attention to it if everything is good.
Nginx could be the server to the user and the client to the backend server like the below:
from user->->nginx->server(tomcat).
In my case, I found that server like tomcat would abort the connection if it cannot handle too many requests in the accepted list.(or too slow to respond).
In tcp, the real server like tomcat would maintain 2 list. The first 1 is SYN list, and the 2nd is accepted list. Pls let me ellaborate it:
Clients firstly send syn to the server.
and the server put it into syn list and return SYN+ACK.
Client send the ACK to the server.
Finally the server established the connection after removing it from the syn list and put it into the accepted list.
In your case, if you close the tab before step2, I think you needn't do anything at all.
if you close the tab before the tab 4, you can refactor the interface of your server to be async to greatly enhance its responding speed.
My understanding so far is that when someone tries to access web page the following happens:
HTTP request is formed
New socket is opened
HTTP request is sent
If everything went OK, the web browser accepts HTTP response and builds DOM tree out of received HTML. If there are any resources missing, new HTTP request needs to be made for each one separately.
Each of those HTTP requests requires opening another socket (establishing new virtual connection with server).
Q: How is that efficient? I understand those resources could be located on another host (which would indeed require new TCP connection) but if they are all on the same host wouldn't it be way more efficient to transfer all data within single TCP connection.
Each of those HTTP requests requires opening another socket (establishing new virtual connection with server).
No it doesn't. HTTP 1.1 uses persistent connections by default, and HTTP 1.0 before it had the unofficial Connection: keep-alive header, which accomplished the same thing, nearly twenty years ago.
Q: How is that efficient?
It isn't, and that's why it doesn't happen.
I understand those resources could be located on another host (which would indeed require new TCP connection) but if they are all on the same host wouldn't it be way more efficient to transfer all data within single TCP connection.
Yes, and that is what happens by default.
I just went through the specification of http 1.1 at http://www.w3.org/Protocols/rfc2616/rfc2616.html and came across a section about connections http://www.w3.org/Protocols/rfc2616/rfc2616-sec8.html#sec8 that says
" A significant difference between HTTP/1.1 and earlier versions of HTTP is that persistent connections are the default behavior of any HTTP connection. That is, unless otherwise indicated, the client SHOULD assume that the server will maintain a persistent connection, even after error responses from the server.
Persistent connections provide a mechanism by which a client and a server can signal the close of a TCP connection. This signaling takes place using the Connection header field (section 14.10). Once a close has been signaled, the client MUST NOT send any more requests on that connection. "
Then I also went through a section on http state management at https://www.rfc-editor.org/rfc/rfc2965 that says in its section 2 that
"Currently, HTTP servers respond to each client request without relating that request to previous or subsequent requests;"
A section about the need to have persistent connections in the RFC 2616 also said that prior to persistent connections every time a client wished to fetch a url it had to establish a new TCP connection for each and every new request.
Now my question is, if we have persistent connections in http/1.1 then as mentioned above a client does not need to make a new connection for every new request. It can send multiple requests over the same connection. So if the server knows that every subsequent request is coming over the same connection, would it not be obvious that the request is from the same client? And hence would this just not suffice to maintain the state and would this just nit be enough for the server to understand that the request was from the same client ? In this case then why is a separate state management mechanism required at all ?
Basically, yes, it would make sense, but HTTP persistent connections are used to eliminate administrative TCP/IP overhead of connection handling (e.g. connect/disconnect/reconnect, etc.). It is not meant to say anything about the state of the data moving across the connection, which is what you're talking about.
No. For instance, there might an intermediate (such as a proxy or a reverse proxy) in the request path that aggregates requests from multiple TCP connections.
See http://greenbytes.de/tech/webdav/draft-ietf-httpbis-p1-messaging-21.html#intermediaries.
I'm newbie in network programming so please forgive me any mistakes.
I'm writing a simple sniffer, which should detect just URLs of websites requested by the user. I'm using pcap.net and I'm able to capture http packets (with tcp port 80 filter) and retrieve data from them. What I can't do is getting a single URI for the request which caused many http packets to come.
For example,
1. a user requests (from a browser) www.website.com
2. many http responses come, one of which is text/html for www.website.com
3. www.website.com contains resources from other html pages, so many other packets from other hosts are coming.
Is there a way to ignore the packets from the resources? Do I have to make some tcp session reconstruction? I've been googling for 2 days but couldn't find anything useful, so please help.
The HTTP responses from other hosts can be identified since they would probably come from different IPs, and not the IP that the request was sent to.
You can match HTTP requests and responses even without full TCP reconstruction by just looking at the IPs and TCP ports.
However, if you have multiple HTTP requests in the same TCP session, you will need to do TCP reconstruction to separate between the different requests and responses.
Can someone explain the difference between the HTTP request and it handling and socket requests on 80 port. As I understood, HTTP server listen the 80 port and when someone sends an HTTP request on this port - server handle it. So when we place socket listener on port 80, and then write HTML formatted message to it - does it means that we send usual HTTP request? But as fiddler said - it false. What's the difference on a packet level? Or another lower than presentation-level between HTTP request and HTTP-formed writing to socket? Thanks.
First of all, port 80 is the default port for HTTP, it is not required. You can have HTTP servers listening on other ports as well.
Regarding the difference between "regular" HTTP requests and the ones you make yourself over a socket - there is no difference. The "regular" HTTP requests you are referring to (made by a web browser for example) are also implemented over sockets, just like you would do it manually yourself. And the same goes for the server. The implementation of the HTTP server listens for incoming socket connections and parses the data that passes there just like you would.
As long as you send in your socket valid HTTP protocol (according to the RFC), there should be no difference in the packet level (if the lower network stack is identical).
Keep in mind that the socket layer is just the layer the HTTP data always passes over. It doesn't really matter who put the data there, it just comes out from the other side the same way it was put in.
Please note that you have some degree of freedom when implementing an HTTP yourself. There are many optional fields and the order of the headers doesn't matter. So it is possible that two different HTTP implementations will be different in the packet level, but will behave basically the same.
The best way to actually see what's going on in the packet level, is by using a network sniffer - like wireshark or packetyzer. A sniffer actually records the packets of the network and shows you their content. So if you record several HTTP implementations (from various browsers) and your own socket implementation, you can make the required changes to make them identical in the packet level.