HTTP persistent connection vs TCP socket connection

http tcp persistent
Kevin Boyd picture Kevin Boyd · Sep 26, 2009 · Viewed 13.6k times · Source

From this article on Wikipedia:

Keepalive messages were not officially supported in HTTP 1.0. In HTTP 1.1 all connections are considered persistent, unless declared otherwise.

  • Does this mean that using this mechanism I can actually simulate a TCP socket connection?
  • Using this can I make a Server "push" data to a client?
  • Are all HTTP connections, even the one I am using to connect to Stack Overflow "HTTP persistent"?
  • Does the COMET technology of server push use this mechanism of HTTP persistent connection to push data to clients?

Answer

Alex Martelli picture Alex Martelli · Sep 26, 2009
  • Does this mean that using this mechanism I can actually simulate a TCP socket connection?

Not really, sockets have MANY more features and flexibility.

  • Using this can I make a Server "push" data to a client?

Not directly, it's still a request/response protocol; the persistent connection just means the client can use the same underlying socket to send multiple requests and receive the respective responses.

  • Are all HTTP connections, even the one I am using to connect to Stack Overflow "HTTP persistent"?

Unless your browser (or a peculiar server) says otherwise, yes.

  • Does the COMET technology of server push use this mechanism of HTTP persistent connection to push data to clients?

Kinda (for streaming, at least), but with a lot of whipped cream on top. There are other Comet implementation approaches, such as hidden iframes and AJAX long polling, that may not require persistent connections (which give some firewalls &c the fits anyway;-).

Related questions

Round Trip Time Http on non persistent, persistent, persistent with pipelining

networking is my final course in my Masters degree. I do have a question regarding how to calculate Round Trip Time of http on non persistent, persistent and persistent with pipelining. After spending countless hours reading regarding the issue, downloading …

Read More
How do multiple clients connect simultaneously to one port, say 80, on a server?

I understand the basics of how ports work. However, what I don't get is how multiple clients can simultaneously connect to say port 80. I know each client has a unique (for their machine) port. Does the server reply back from …

Read More
Can I use tcpdump to get HTTP requests, response header and response body?

I am using tcpdump to get HTTP data by executing the below command: sudo tcpdump -A -s 1492 dst port 80 The result of above command: Headers, I think request and response headers. Unreadable data. The url GET /modules/mod_news_pro_…

Read More