What happens when the browser window enters the URL (http full request)

1, DNS query get IP

The input is the domain name, need to do DNS resolution to IP, the approximate process:

• If the browser has a cache, use the browser cache directly, otherwise use the native cache, and then do not have to use the host

• If there is no local, the DNS domain name server query (of course, the middle may also be routed, there are caches, etc.), query to the corresponding IP

2. TCP/IP Request

The essence of HTTP is the tcp/ip request.

Need to know 3 handshake rules to establish a connection and four waves when disconnecting.

TCP divides HTTP long messages into short messages, and connects to the server via three handshake to reliably transmit.

3, three steps to shake hands (abstract pie)

• Client: Hello, are you server?

• Service side: Hello, I am server, are you a client?

• Client: Yes, I am client

Once the connection is established, the data is then formally transferred.

Then, until you disconnect, you need to wave four times.

4, four waves of steps (abstract pie)

• Active side: I have closed the active channel to your side, can only passively receive

• Passive side: Receive channel shutdown information

• Passive side: Well, I'm telling you, my side is closed to your Active channel.

• Active: The last data received, then the two sides can not communicate

What happens when the browser window enters the URL (http full request)