一个“ a”时间有多少个请求可以处理一个端口

Question

I am creating a web application having a login page , where number of users can tries to login at same time. so here I need to handle number of requests at a time.

I know this is already implemented for number of popular sites like G talk .

So I have some questions in my mind.

"How many requests can a port handle at a time ?"

How many sockets can I(server) create ? is there any limitations?

For eg . As we know when we implement client server communication using Socket programming(TCP), we pass 'a port number(unreserved port number)to server for creating a socket .

So I mean to say if 100000 requests came at a single time then what will be approach of port to these all requests.

Is he manitains some queue for all these requests , or he just accepts number of requests as per his limit? if yes what is handling request limit size of port ?

Summary: I want to know how server serves multiple requests simultaneously?I don't know any thing about it. I know we are connection to a server via its ip address and port number that's it. So I thought there is only one port and many request come to that port only via different clients so how server manages all the requests?

This is all I want to know. If you explain this concept in detail it would be very helpful. Thanks any way.

Answer 1

A port doesn't handle requests, it receives packets. Depending on the implementation of the server this packets may be handled by one or more processes / threads, so this is unlimited theoretically. But you'll always be limited by bandwith and processing performance.

If lots of packets arrive at one port and cannot be handled in a timely manner they will be buffered (by the server, the operating system or hardware). If those buffers are full, the congestion maybe handled by network components (routers, switches) and the protocols the network traffic is based on. TCP for example has some methods to avoid or control congestion: http://en.wikipedia.org/wiki/Transmission_Control_Protocol#Congestion_control

Answer 2

This is typically configured in the application/web server you are using. How you limit the number of concurrent requests is by limiting the number of parallel worker threads you allow the server to spawn to serve requests. If more requests come in than there are available threads to handle them, they will start to queue up. This is the second thing you typically configure, the socket back-log size. When the back-log is full, the server will start responding with "connection refused" when new requests come in.

Answer 3

Then you'll probably be restricted by number of File Descriptors your os supports (in case of *nix) or the number of simultaneous connections your webserver supports. The OS maximum on my machine seems to be 75000.

Answer 4

100,000 concurrent connections should be easily possible in Java if you use something like Netty .

You need to be able to:

• Accept incoming connections fast enough. The NIO framework helps enormously here, which is what Netty uses internally. There is a smallish queue for incoming requests, so you need to be able to handle these faster than the queue can fill up.
• Create connections for each client (this implies some memory overhead for things like connection info, buffers etc.) - you may need to tweak your VM settings to have enough free memory for all the connections

See this article from 2009 where they discuss achieving 100,000 concurrent connections with about 20% CPU usage on a quad-core server.