Python Network Programming Study Notes (5): Supplement to socket

I have already introduced some knowledge about pythonsocket. Here I would like to add some suggestions for you to make it easier. 1. semi-open socket

Use the shutdown () function to convert two-way socket data transmission to one-way data transmission. Shutdown () requires a separate parameter, which indicates how to close the socket. Specifically: 0 indicates that future reading is prohibited; 1
Indicates that future writing is prohibited; 2 indicates that future reading and writing are prohibited.

2. timeouts control timeout

Call the settimeout () function of the socket and pass a parameter to it, indicating the timeout setting. When a socket is accessed, if nothing happens after the time specified by the parameter, a socket. timeout exception is generated.
For example, when the program runs, it will wait for data to be passed in. Use telnet to connect to port 12345 on another terminal. After the connection is successful, "connection from: *****" is displayed. If no input is made from the terminal within five seconds
The system prompts that the connection times out and exits.

The Code is as follows:

The Code is as follows:

#-*-Coding: cp936 -*-
# Tcp response Server
Import socket, traceback
Host =''
Port = 12345
S = socket. socket (socket. AF_INET, socket. SOCK_STREAM)
S. setsockopt (socket. SOL_SOCKET, socket. SO_REUSEADDR, 1)
S. bind (host, port ))
S. listen (1)

While 1:
Try:
Clientsock, clientaddr = s. accept ()
Except t KeyboardInterrupt:
Raise
Except t:
Traceback. print_exc ()
Continue
Clientsock. settimeout (5)
Try:
Print "connection from:", clientsock. getpeername ()
While 1:
Data = clientsock. recv (4096)
If not len (data ):
Break
Clientsock. sendall (data)
Clientsock. sendall ("\ nI get it! \ N ")
# T = raw_input ('input the word :')
# Clientsock. sendall (t)
Except T (KeyboardInterrupt, SystemExit ):
Raise
Failed t socket. timeout:
Print 'Connection timeout'
Pass
Except t:
Traceback. print_exc ()

Try:
Clientsock. close ()
Except t KeyboardInterrupt:
Raise
Except t:
Traceback. print_exc ()

3. Understand the network byte sequence

Different platforms have different binary data encoding methods. To solve this problem, a standard binary data representation is called the network byte sequence. Before sending a binary integer, the integer is
To the byte sequence of the network. After receiving the data, the receiver first converts the network bytes to the local representation cost.
The python struct module supports data conversion between python and binary data.
There are two basic formats:
H: Applicable to 16-digit integers
I: Applicable to 32-bit Integers
The exclamation point indicates that the struct module uses the network byte sequence for encoding and decoding. Other formats are shown in the following table:

Character	Byte order	Size and alignment
@	Native	NativeEnough4Bytes
=	Native	StandardBy the number of original bytes
<	Little-endian	StandardBy the number of original bytes
>	Big-endian	StandardBy the number of original bytes
!	Network (= big-endian)	StandardBy the number of original bytes

Common statements:

Struct. pack (fmt, v1, v2,...) converts v1 and v2 according to the parameter format. The fmt parameter is a format character.
String, here mainly! I. V1, v2,... indicates the python value to be converted.
Struct. unpack (fmt, string) is the opposite of pack.
For example:

>>> Import struct
>>> A = 20
>>> Str = struct. pack ("! I ",)
>>> Print repr (str)
'\ X00 \ x00 \ x00 \ x14'
>>> Print struct. unpack ("! I ", str)
(20 ,)