The Internet ：
Network protocol ： A set of rules
Network model seven layer model - Seven layers The physical layer Data link layer The network layer Transport layer The session layer The presentation layer Application layer four layer model The link layer The network layer Transport layer application layer
Each layer has its own protocol for information exchange or collaboration
TCP/IP agreement Protocol family
IP Address ： Responsible for locating the only machine on the network IP The address is divided into 5 class 3 spot 4 Paragraph style , Each field is 0~255127.0.0.1： This machine IPV4 IPV6
Port number range ：0-65535 Well known ports ：0——1023 Already known ports Unknown port ：1024->
UDP： Non secure, non link oriented transport
Poor safety
Size limit 64kb
There is no order
Fast
TCP
Link based communication
SOCKET Programming
socket（ Socket ）： This is an endpoint for network communication , Realize the process communication of different hosts
adopt IP+ The communication mechanism by which ports locate each other and send messages
It is divided into UDP and TC P
UDP Programming Server End process
1. establish socket.socket Is an example of a specific communication
2. binding , Create for socket Assign fixed ports and IP Address
3. Accept the content sent by the other party
4. Send feedback ,
This step is not required Client End process ：
1. Establish communication socket
2. Send content to the specified server 3
. Receive feedback from the server
Server case V01
import socket
def serverFunc():
#AF_INET Use IPv4 agreement SOCK_DGRAM Use UDP agreement
soc = socket.socket(socket.AF_INET,socket.SOCK_DGRAM)
# binding IP And port number
addr = ('127.0.0.1',10089)
soc.bind(addr)
# Be interviewed
data,addr = sco.recvfrom(500)
print(data)
# The data needs to be decoded before it can be read
data = data.deconde()
print(data)
# Feedback to the other person
res = ' Feedback '
# Encode and send the data
res = res.encode()
soc.sendto(res,addr)
if __name__ == "__main__":
print('Start Server...')
serverFunc()
print('End Server.....')
Client case V02
import socket
def clientFunc():
soc = socket.socket(socket.AF_INET,socket.SOCK_DGRAM)
text = ' Access from the client '
data = text.encode()
soc.sendto(data,('127.0.0.1',10089))
data,addr = socket.recvfrom(200)
data = data.decode()
print(data)
if __name__ == '__main__':
print("client...")
clientFunc()
print("end client...")
The server requires a permanent run case V03
import socket
import time
def serverFunc():
soc = socket.socket(socket.AF_INET,socket.SOCK_DGRAM)
addr = ('127.0.0.1',10089)
soc.bind(addr)
data,addr = soc.recvfrom(500)
data = data.decode()
print(data)
res = ' Feedback from the server '
res = res.encode()
soc.sendto(res,addr)
if __name__ == '__main__':
print('Start Server..')
while True:
try:
serverFunc()
except Exceptiom as e:
print(e)
time.sleep(1)
print('end Server...')
TCP Programming
Link oriented transport , And the connection needs to be established before each transmission
Both client and server programs need to be written
Server End of the writing process ：
1. establish socket Responsible for specific communications , This socket In fact, it is only responsible for accepting the request of the other party
2. Bind port number and address
3. Monitor access socket
4. Visited socket, It is understandable that accepting access establishes a communication connection .
5. Accept the content sent by the other party , Use what you receive socket Receiving content
6. If necessary , Send feedback
7. Close links
# Import package
import socket
def TCP_Server():
#AF_INET Use IPV4 agreement ,SOC_STREAM Use TCP
soc = socket.socket(socket.AF_INET,sockey.SOC_STREAM)
addr = ('127.0.0.1',10089)
# Binding address and port number
soc.bind(addr)
# Monitor the network
soc.listen()
while True:
# The return value is the content and link address
skt,addr = soc.accept()
msg = skt.recv(500)
data = msg.decode()
rest = "recvide msg : {0} from {1}".formate(data,addr)
print(rest)
skt.send(rest.encode())
skt.close()
if __name__ == "__main__":
print("Start Server...")
TCP_Server()
Client End process ：
1. Establishing communication socket
2. Link to each other , Request remote link with the other party
3. Send content to the other server
4. Accept feedback from others
5. Close the connection case of the link V04 V05
import socket
def TCP_Clinet():
sock = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
addr = ('127.0.0.1',10089)
scok.bind(addr)
msg = " This is one hop client information "
sock.send(msg.encode)
res = sock.recv(500)
print(res.decode)
sock.close()
if __name__ == "__main__":
TCP_Client()
FTP(FileTransferProtocal) File transfer protocol
purpose ： Customize some special services for loading and downloading files
The user classification ： land FTP The server needs an account
Real： Account
Guest： It can authorize the behavior of a certain class of people temporarily
Anonymous： Anonymous accounts , Allow anyone to .
FTP Workflow
The client Links... On the remote host FTP The server
The client enters the user name and password （ perhaps “anonymous” And email address ）
Client and server carry out various file transfer and information query operations
Client from remote server FTP sign out , End transmission
FTP Representation of documents
In three paragraphs FTP Files on the server
HOST： The host address , Be similar to ftp.mozilla.org, With FTP start
DIR： Directory indicates the local path where the file is located
File： File name
If you want a complete and accurate representation ftp Last file , The above three parts need to be combined .- Case study V06
# Import the corresponding package
import ftplib
import os
import socket
# The three steps represent precise ftp A file on the server
HOST = 'ftp.acc.umu.se'
DIR = 'Public/EFLIB/'
FILE = 'README'
# Remote Links FTP The server
try:
f = ftplib.FTP()
f.set_debuglevel(2)
f,connect(HOST)
except Exception as e:
print(e)
exit()
print("******Connect to hsot {0}".formate(HOST))
# Login server
try:
f.login()
except Expetion as e:
print(e)
exit()
print("login in sa 'anonymouse'")
# Change the current directory after successful login
try:
f.cwd(DIR)
except Exception as e:
print(e)
exit()
print("***change dir to {0}".formate(DIR))
# Download the corresponding file after switching directories
try:
# from FTP Download files on
# The first parameter is FTP command
# The second parameter is the callback function
# This function must refer to , perform RETR command , After downloading the file to the local , Running callback function
f.retrbinary('RETR {0}'.formate(FILE),open(FILE,"wb").write)
except Exception as e:
print(e)
exit()
# Link out
f.quit()
