An example of Python socket programming: simulating various common winerror situations

example python socket programming simulating


One 、 introduction

Recently, I used Python Wrote a little tool for testing , Maybe it works like this :

This gadget works as a server , Request information from the client , Do something about it , Then return the message synchronously or asynchronously .

For this gadget , It mainly works as the server of the requested service . And in the development of this gadget , I often encounter things like Python Socket programming [WinError XXXXX] Or something like that .

I've met a lot , I find , Instead of meeting a WinError Error and search for the reason , Let's write a simple one based on TCP The server-side client communication program of , Come and take these by yourself WinError The wrong situation is simulated , such , We're going to treat these as well WinError Mistakes have a deeper understanding .

Do what you say , First, the simplest use of Python Socket The server-side client communication program realized by programming . then , We build on this code , All kinds of operations , To simulate the implementation of some common WinError error .

Two 、C&S Code

here , Go straight to the code :

1. Code

Server program

"""
Client side
Author: Wang Ying
Last modified: July 30 2019
"""
from socket import socket, AF_INET, SOCK_STREAM
# Create socket
tcpSerSocket = socket(AF_INET, SOCK_STREAM)
# Bind ip & port
address = ('127.0.0.1', 9999)
tcpSerSocket.bind(address)
# Begin listen
tcpSerSocket.listen(5)
while True:
# Receive client's connect, newSocket is served for client.
# tcpSerSocket wait for another client's connect.
newSocket, clientAddr = tcpSerSocket.accept()
while True:
# Receive client data
recvData = newSocket.recv(1024)
# if data length is 0, just break
if len(recvData) > 0:
print('recv:', recvData)
else:
break
# Send some data to client
sendData = input("send:")
newSocket.send(bytes(sendData.encode('utf-8')))
# Close the client socket
newSocket.close()
# Stop listen
tcpSerSocket.close()

Client program

"""
Client side
Author: Wang Ying
Last modified: July 30 2019
"""
from socket import socket, AF_INET, SOCK_STREAM
# Create socket
tcpClientSocket = socket(AF_INET, SOCK_STREAM)
# Connect to server
serAddr = ('127.0.0.1', 9999)
tcpClientSocket.connect(serAddr)
while True:
# Prompt input
sendData = input("send:")
if sendData == 'bye':
break
if len(sendData) > 0:
tcpClientSocket.send(bytes(sendData.encode('utf-8')))
else:
break
# Receive server data
recvData = tcpClientSocket.recv(1024)
print('recv:', recvData)
# Close socket
tcpClientSocket.close()

2. analysis

about Socket Programmatically , All languages are the same ,Python No exception . In this case :

The server side program is bound with a 9999 port , Then listen to the client socket The connection of . The two floors here while loop , The outer layer is used to traverse the connection requests of multiple clients , The inner layer is used to realize the interaction with the client to receive and send data .

The client program connects to the server port , And then you go into a loop , Used to send data to the server .

here , First run the server side program , Then run the client program , The client sends the message first , Server received , Then the server sends the message to the client , Client received , The client can continue to send messages to the server … until , Client input bye, Then jump out of the loop , Close the client's socket Connect , And that's the end of the process .

1

This is a very simple server-side client communication program , We can use this program to simulate all kinds of WinError error . Let's start next :)

3、 ... and 、 experiment

[WinError 10061] Because the target computer actively refuses , Unable to connect

We just said , Run this program , You need to run the server program first , Then run the client program , This is because the server monitors first , Then the client will connect to .

that , If the server program is not started first , At this point, the client runs , What kind of mistakes will happen ?
2
Sum up :

Once the client starts , The server does not want to connect on the client side IP And port number , Then there will be [WinError 10061] Because the target computer actively refuses , Unable to connect Error of .

[WinError 10054] The remote host forced an existing connection to be closed

Let's run the server program first , Then run the client program , And then the client program will be forced to kill ( Don't let it shut down properly socket Connect ), What kind of mistakes will occur at this time ?

3
This mistake is easy to understand , Connected to socket The connection is forcibly interrupted by the other party ( abnormal close Dropped ), This error will appear .

Some netizens may feel that , Here is the client force kill , So what's wrong with killing the server ? ha-ha , You can try it yourself , The answer is no mistake :) why , You can think for yourself , Here's just a hint , A client only connects to one server , But a server , It is to connect zero one or more clients .

Sum up :

When the client connects to the server , The client program is forced to kill , At this point, the server will report an error [WinError 10054] The remote host forced an existing connection to be closed

[WinError 10048] Usually every socket address ( agreement / network address / port ) Only one use is allowed

Let's modify the client code a little bit , Try not to let the client go connect Server side socket Connect , It is bind( It's like the server ), Revised as follows :
client.py

tcpClientSocket.connect(serAddr)
# It is amended as follows 
tcpClientSocket.bind(serAddr)

What's the problem ?

4
In fact, this is also very easy to understand , After all, the same port is monitored by two programs , There is bound to be a port occupancy problem .

Sum up :

A port has been occupied , And then another program wants to use it , There will be errors [WinError 10048] Usually every socket address ( agreement / network address / port ) Only one use is allowed

[WinError 10038] An operation was attempted on a non socket

We're going to change the code this time , This time we modify the server-side code :
server.py

 while True:
...
# 2. This call close, Leading to the next cycle recv Of 
# When you use a closed socket Connect 
# Receive data 
newSocket.close()
# 1. It should have been closed after jumping out of the loop socket, We are now 
# After receiving the client's return , Shut it down immediately . Analog off 
# close socket And then receive socket Data scenario .
# newSocket.close()

What we modified is server.py, The original close The function is put inside the loop , Lead to close Then I call once recv. Let's run the server program first , Then run the client program to see what happens :
1
We found that , On the server side, the program runs to recv When it comes to [WinError 10038] An operation was attempted on a non socket Error of , Actually, it's easy to understand , Because after all, you've put this socket The connection is closed , And then you want to use it to receive data .

To sum up :

When you shut down a socket Connect (close), And then use that socket Object receives data (recv), There will be an error [WinError 10038] An operation was attempted on a non socket

... To be continued , Keep updating

If in the follow-up work , There are other interesting error messages , I'll also come here to keep updating :)

Four 、 summary

Study Python Ben is a very happy thing , Happier than it is , That's using Python The process of .

Python The way , The road is long but not boring ~~~
To be Stronger:)

版权声明
本文为[I've been to places that span an hour]所创,转载请带上原文链接,感谢

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