Python in the HTTP protocol (notes)

1. Introduction http protocol
   HTTP, HyperText Transfer Protocol. Hypertext Transfer Protocol, is the Internet's most widely used network protocol. TCP-based protocol, HTTP is a client and server side request and response standard
2. TCP three-way handshake
   
   SYN is synchronization request means, Acronym synchronize (Sync) of the
   ACK is confirmed that the synchronization is, Acknowledgment (confirmation) Abbreviation
   TCP host transmission control protocol of the host layer provides a reliable connection service
   TCP three-way handshake
   the first handshake :( client: the server it)?
   establish a connection, the client A occurs SYN packet (SYN = j) to server B
   and enter SYN_SEND state, waiting for the server B confirms
   second handshake :( server: close to, in the,)
   server B receives the SYN packet, the client a must confirm the SYN, ACK = j + 1
   at the same time he is sending a SYN packet, SYN = k
   i.e., SYN + ACK packet, then the server enters a state SYN_RECV
   of client :( three-way handshake: I want to send the data)
   client a server B receives SYN + ACK packet
   sends an acknowledgment to the server B packet ACK (ACK = k + 1)
   of this packet been sent, the client and the server a B enters ESTABLISHED state, complete the three-way handshake
3. TCP four waved process
   
   Client A sends a FIN to close the client A to server B data transmission (segment 4) (Client: I want to shut up).
   The server B receives the FIN it sends back an ACK , +1 acknowledgment number of the received sequence number (segment 5). And SYN as a FIN will take a number (server: OK, you receive)
   connected to the server A and B closed the client, the client sends a FIN (6 segments) (server A: I have off)
   client a sends back an ACK acknowledgment message, the acknowledgment number and the set number plus 1 (segment 7) (client: good, received)
4. How to reuse the same port server without prompting port is occupied
   tcp_server_socket.setsockopt (socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
   allow address reuse
5. str.splitlines () in rows ( '\ r', '\ n', '\ r \ n') separated, it returns a list of elements as each row