One Basic knowledge of

Before code implementation , Let's start with a brief introduction TCP,UDP,Socket And so on .

First of all, understand socket（ Socket ）, We can go through " Socket " Send a request to the network or answer a network request , To enable communication between hosts or processes on a computer .

In addition, in the communication , We use it a lot TCP and UDP,TCP,UDP Connections belonging to the transport layer , The difference between them is TCP It's link oriented , His connection requires three handshakes ; and UDP No connection is established with the other party before data transmission . So generally speaking TCP Than UDP Security , however UDP Than TCP real time .

HTTP Protocols belonging to the application layer , Only the connection transmits data , But without a protocol, we don't know what the transmission is , So we need an application layer HTTP agreement （ Hypertext Transfer Protocol Hypertext Transfer Protocol ）.TCP It's the underlying communication protocol , It defines the specification of data transmission and connection mode ;HTTP It's the application layer protocol , What is defined is the specification of the content of the transmitted data ;

We have a connection , You also need an external interface , This is what this article will introduce Socket Socket .Sockert The programming interface is to make it easier for us to use the protocol stack .

Specific introduction can refer to ：

TCP and UDP The difference and HTTP agreement

https://segmentfault.com/a/1190000014044351

Socket Connect with HTTP Connect

https://cloud.tencent.com/developer/article/1124905

Two Code example

Let's use python Of Socket Programming , Simple implementation of a client to send requests , After receiving the request, the server returns a json An example of .

The library you need is

import socket

Server code

What the server mainly does

1. Create socket ：socket.socket()
2. binding IP And port ：socket.bind()
3. Start tcp monitor socket.listen()
4. Accept tcp Connect , Waiting for data ：socket.accept()
5. receive data ：socket.recv()
6. Send processing data ：socket.sendall()
7. Close socket ：socket.close()

among recv and send yes bytes type , So if it's a string or json Format needs to be down converted . Because the project uses json Format , So this article also received str, return json Write examples in the form of .

The detailed code of the server is as follows ：

import json
import socket
HOST = '127.0.0.1'
PORT = 8000
ADDR = (HOST,PORT)
def start_server():
# Create socket ：AF_INET-- Use ipv4 Address family SOCK_STREAM-- Use streaming sockets
svr_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
svr_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
# binding host:port
svr_socket.bind(ADDR)
# setblocking 0-- Non-blocking mode ,1-- Blocking mode The default is 1
svr_socket.setblocking(1)
# Start listening TCP Incoming connections
svr_socket.listen(5)
# Return the new socket and client address
client_socket, addr = svr_socket.accept()
client_socket.settimeout(20.0)
# receive data , Here, the data length is received first （ You need to negotiate the sending format with the client , Whether it is len+data In the form of ）, You don't have to do this
data_len = client_socket.recv(4)
length = int.from_bytes(data_len, byteorder="big")
# Specific data received , You can also set a larger buffer here
data = client_socket.recv(length)
print("rev client data", data)
# Data returned to the client , Set to a json
json_msg ={"key":"id","val": 123}
str_msg = json.dumps(json_msg)
# The string should be converted to bytes transmission
client_socket.sendall(str_msg.encode())
# Close socket
client_socket.close()
if __name__ == '__main__':
start_server()

Client code

What the server mainly does

1. Create socket ：socket.socket()
2. open tcp Connect ：socket.connect()
3. Send request data ：socket.sendall()
4. Receive server data ：socket.recv()
5. Close socket ：socket.close()

Complete code ：

import json
import socket
HOST = '127.0.0.1'
PORT = 8000
ADDR = (HOST,PORT)
def start_client():
# Create socket
_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
# open tcp Connect
_socket.connect(ADDR)
msg = "msg from client"
length = len(msg)
buf = length.to_bytes(4, byteorder="big")
# Send request data len+data Format
_socket.sendall(buf + msg.encode())
# The receiving server returns data
data = _socket.recv(1024)
msg = json.loads(data)
print("client get json", msg)
# Close socket
_socket.close()
if __name__ == '__main__':
start_client()