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Writing a WEB server from scratch

We do not want to re-invent the wheel, and we will use a WEB server framework already prepared for us by professional programmers. It is nevertheless interesting to implement a very primitive WEB server ourselves, simply to understand the basic principles.

The Hello World WEB Server

Let's start simple and produce a WEB server that just sends "Hello World!" to the browser when called. You may add some HTML text if desired. In the first version we will write a TCP server creating a stream socket and binding to port 80.

s=socket.socket(socket.AF_INET,socket.SOCK_STREAM) 
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) 
try:
    s.bind(('',80)) 
except OSError as exception:      
    if exception.args[0] = uerrno.EADDRINUSE:
          print("Socket is already bound, please reset the machine") 
          sys.exit()

The server then starts listening for an incoming connection request and establishes a connection by accepting it.

s.listen(5) 
print("Starting the Hello World WEB server on IP address ",ipaddr,"port 80")
while True: 
    conn,addr=s.accept()     print("GOT a connection from %s" % str(addr))

Finally, it reads an HTTP request from the connection and answers with its Hello World page:

request=conn.recv(1024)
print("Content %s" % str(request))
request=str(request) 
response=html 
conn.send(response) 
conn.close()

HTML is the HTTP string to be sent, e.g.

html = """ <!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body>
<title>Hello World </title>
<h1>The Hello World! HTML page</h1>
<p>Hello World!</p>

</body>
</html> 
"""

Please check https://docs.micropython.org/en/latest/library/usocket.html for more details.

Here is the complete program:

https://iotworkshop.africa/pub/IoT_Course_English/BasicWEBServer/helloWorldWebServerV1.py.txt

-- Uli Raich - 2020-06-08

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Topic revision: r3 - 2022-11-12 - UliRaich