122 lines
3.8 KiB
ReStructuredText
122 lines
3.8 KiB
ReStructuredText
Network - TCP sockets
|
|
=====================
|
|
|
|
The building block of most of the internet is the TCP socket. These sockets
|
|
provide a reliable stream of bytes between the connected network devices.
|
|
This part of the tutorial will show how to use TCP sockets in a few different
|
|
cases.
|
|
|
|
Star Wars Asciimation
|
|
---------------------
|
|
|
|
The simplest thing to do is to download data from the internet. In this case
|
|
we will use the Star Wars Asciimation service provided by the blinkenlights.nl
|
|
website. It uses the telnet protocol on port 23 to stream data to anyone that
|
|
connects. It's very simple to use because it doesn't require you to
|
|
authenticate (give a username or password), you can just start downloading data
|
|
straight away.
|
|
|
|
The first thing to do is make sure we have the socket module available::
|
|
|
|
>>> import socket
|
|
|
|
Then get the IP address of the server::
|
|
|
|
>>> addr_info = socket.getaddrinfo("towel.blinkenlights.nl", 23)
|
|
|
|
The ``getaddrinfo`` function actually returns a list of addresses, and each
|
|
address has more information than we need. We want to get just the first valid
|
|
address, and then just the IP address and port of the server. To do this use::
|
|
|
|
>>> addr = addr_info[0][-1]
|
|
|
|
If you type ``addr_info`` and ``addr`` at the prompt you will see exactly what
|
|
information they hold.
|
|
|
|
Using the IP address we can make a socket and connect to the server::
|
|
|
|
>>> s = socket.socket()
|
|
>>> s.connect(addr)
|
|
|
|
Now that we are connected we can download and display the data::
|
|
|
|
>>> while True:
|
|
... data = s.recv(500)
|
|
... print(str(data, 'utf8'), end='')
|
|
...
|
|
|
|
When this loop executes it should start showing the animation (use ctrl-C to
|
|
interrupt it).
|
|
|
|
You should also be able to run this same code on your PC using normal Python if
|
|
you want to try it out there.
|
|
|
|
HTTP GET request
|
|
----------------
|
|
|
|
The next example shows how to download a webpage. HTTP uses port 80 and you
|
|
first need to send a "GET" request before you can download anything. As part
|
|
of the request you need to specify the page to retrieve.
|
|
|
|
Let's define a function that can download and print a URL::
|
|
|
|
def http_get(url):
|
|
_, _, host, path = url.split('/', 3)
|
|
addr = socket.getaddrinfo(host, 80)[0][-1]
|
|
s = socket.socket()
|
|
s.connect(addr)
|
|
s.send(bytes('GET /%s HTTP/1.0\r\nHost: %s\r\n\r\n' % (path, host), 'utf8'))
|
|
while True:
|
|
data = s.recv(100)
|
|
if data:
|
|
print(str(data, 'utf8'), end='')
|
|
else:
|
|
break
|
|
|
|
Make sure that you import the socket module before running this function. Then
|
|
you can try::
|
|
|
|
>>> http_get('http://micropython.org/ks/test.html')
|
|
|
|
This should retrieve the webpage and print the HTML to the console.
|
|
|
|
Simple HTTP server
|
|
------------------
|
|
|
|
The following code creates an simple HTTP server which serves a single webpage
|
|
that contains a table with the state of all the GPIO pins::
|
|
|
|
import machine
|
|
pins = [machine.Pin(i, machine.Pin.IN) for i in (0, 2, 4, 5, 12, 13, 14, 15)]
|
|
|
|
html = """<!DOCTYPE html>
|
|
<html>
|
|
<head> <title>ESP8266 Pins</title> </head>
|
|
<body> <h1>ESP8266 Pins</h1>
|
|
<table border="1"> <tr><th>Pin</th><th>Value</th></tr> %s </table>
|
|
</body>
|
|
</html>
|
|
"""
|
|
|
|
import socket
|
|
addr = socket.getaddrinfo('0.0.0.0', 80)[0][-1]
|
|
|
|
s = socket.socket()
|
|
s.bind(addr)
|
|
s.listen(1)
|
|
|
|
print('listening on', addr)
|
|
|
|
while True:
|
|
cl, addr = s.accept()
|
|
print('client connected from', addr)
|
|
cl_file = cl.makefile('rwb', 0)
|
|
while True:
|
|
line = cl_file.readline()
|
|
if not line or line == b'\r\n':
|
|
break
|
|
rows = ['<tr><td>%s</td><td>%d</td></tr>' % (str(p), p.value()) for p in pins]
|
|
response = html % '\n'.join(rows)
|
|
cl.send(response)
|
|
cl.close()
|