I am currently developing a system where I need to send notification to Raspberry to run a Python file. It is much like a observer pattern design where my server is publisher and Raspberry is the observer. Worth to note that, I actually need to interact with one Raspberry at the time (even I have dozens of them). Specifically, on a specific event, I need to warn a single Raspberry that it has to take an action.
I searched for it literally for all the night but I could not find anything coming handy. Nothing really give me a clue how to implement this.
The most close answer I could find is this technology firm's product called PubNub which can actually work. However, as I need is a one-to-one interaction, this might be unnecessary because it is designed to publish a data to multiple clients.
Long story short, I need to trigger Raspberry to take some action in accordance to the some data coming from the server, whenever it receives the data.
Server is running on Amazon and implemented with Python 2.7.
Please do not hesitate to ask me for further detail, if I am missing any.
Thanks for all the supports,
EDIT
Just a recent update with an improvement to my answer. As far as I understand, sockets are able to manage this process. Such as from client (Raspberry in my case) listening for the server and server sending some data. Taken from this site, I managed to make a sample run on my computer, from my local. I used Port 5000 as their 'meeting point'.
Below is the code:
client.py
#!/usr/bin/env python
import socket
TCP_IP = '127.0.0.1'
TCP_PORT = 5000
BUFFER_SIZE = 1024
MESSAGE = b"Hello, World!"
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((TCP_IP, TCP_PORT))
s.send(MESSAGE)
data = s.recv(BUFFER_SIZE)
s.close()
print("received data:", data)
server.py
#!/usr/bin/env python
import socket
TCP_IP = '127.0.0.1'
TCP_PORT = 5000
BUFFER_SIZE = 20 # Normally 1024, but we want fast response
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((TCP_IP, TCP_PORT))
s.listen(1)
conn, addr = s.accept()
print('Connection address:', addr)
while 1:
data = conn.recv(BUFFER_SIZE)
if not data: break
print("received data:", data)
conn.send(data) # echo
conn.close()
However, I still have some questions.
Firstly, I want to learn whether the same thing work when I deploy the project and how. If that will work - lets say I have an url for the server like 'www.thisisanexampleurl.com' - simply assignign a port for it, will work?
Secondly, assuming first question is done, what is the way of making it continous so that it does not stop after receiving and sending data once. Because currently, when it makes the data transfer, it stops working.
Thanks again for the all support and again please do not hesitate to ask me for the further details i am missing any.
You should be able to do something this simple:
Run something like this on your pi:
import socket
s = socket.socket()
host = ""
port = 12345
s.bind((host, port))
s.listen(5)
while True:
try:
clientsock, addr = s.accept()
except OSError:
continue
message = clientsock.recv(20)
#the code you want to run
print("doing %s" % message)
clientsock.close()
And this on your server every time you want the pi to take action:
import socket
s = socket.socket()
host = "0.0.0.0"
port = 12345
s.connect((host, port))
s.send("foo")
s.close()
Have a look at Pyro4. It lets you avoid having to write network code at all and just write code that calls remote Python objects as if they were running on the same machine. In your case, the server could call a normal Python method on your Raspberry Pi to do something. It has many features but you can start with something extremely simple.
raspberry pi code:
import Pyro4
#Pyro4.expose
class Raspberry:
def something(self, arg):
print("called with:", arg)
return "hi from pi"
Pyro4.Daemon.serveSimple({Raspberry: "raspberry"})
server code to make the pi do something:
import Pyro4
rasp = Pyro4.Proxy("PYRONAME:raspberry")
print(rasp.something(42))
Related
I am looking to learn if you know of any python libraries or methodologies that would allow me to do the following.
I am looking to run two python scripts, sender & receiver. I would like each to run on separate machines in Python. I want the sender to pass a data string to receiver over the internet.
Any idea on how I can do this?
Much appreciated!
If you want to accomplish this task you need to take a look at the python socket.py module (https://docs.python.org/3/library/socket.html).
An example for a sender script from (https://www.geeksforgeeks.org/socket-programming-python/):
# first of all import the socket library
import socket
# next create a socket object
s = socket.socket()
print ("Socket successfully created")
# reserve a port on your computer in our
# case it is 12345 but it can be anything
port = 12345
# Next bind to the port
# we have not typed any ip in the ip field
# instead we have inputted an empty string
# this makes the server listen to requests
# coming from other computers on the network
s.bind(('', port))
print ("socket binded to %s" %(port))
# put the socket into listening mode
s.listen(5)
print ("socket is listening")
# a forever loop until we interrupt it or
# an error occurs
while True:
# Establish connection with client.
c, addr = s.accept()
print ('Got connection from', addr )
# send a thank you message to the client. encoding to send byte type.
c.send('Thank you for connecting'.encode())
# Close the connection with the client
c.close()
# Breaking once connection closed
break
An example for a reciever script that can be run on the same machine or another machine:
# Import socket module
import socket
# Create a socket object
s = socket.socket()
# Define the port on which you want to connect
port = 12345
# connect to the server on local computer
s.connect(('127.0.0.1', port))
# receive data from the server and decoding to get the string.
print (s.recv(1024).decode())
# close the connection
s.close()
Here in the two examples the two scripts were running on the same machine but you can change that.
This document can be helpful too (https://docs.python.org/3/howto/sockets.html)
A little summary, i programm a socket server in python to fetch data from my MSSQL database and send it to my Flutter App. So far so good. Now i tried to test it from outside. I set a Port Forwarding and tried to connect it. btw it works fine. I let the server run for few hours and now i get a error messenge.
See the pic, the first ip is mine but the second is not.
Someone is trying to connect to my server. How do solve this Problem
MY Python Code
from datetime import datetime
import socket
from SqlServerRequest import SqlServerRequest
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind(('192.168.43.126', 2222))
s.listen(5)
while True:
clientsocket, address = s.accept()
print(f"Connection from {address} has been established.")
data = clientsocket.recv(2048).decode()
print(data)
if data == "open":
o = SqlServerRequest.dataForOpenOrders()
clientsocket.sendall(bytes(o,"utf-8"))
if data == "closed":
c = SqlServerRequest.dataForClosedOrders()
clientsocket.sendall(bytes(c,"utf-8"))
clientsocket.close()
Well, you did set up port forwarding to allow anyone on the internet to connect to your machine. Someone just did, and sent something to your program that it didn't expect, and your program crashed.
That's a great lesson on making your program robust in the face of unexpected input, for instance.
Secondly, if you want your program to actually be accessible on the internet, you will probably want some sort of authentication -- for instance, a password known by your Flutter client.
Likely on top of that, you'd want some sort of transport-layer security so people can't read your data in-flight.
The crash happens because you're trying to convert to Unicode. If this is really all there is, then it's silly to convert to Unicode at all. Just leave it as a bytes string.
wwhile True:
clientsocket, address = s.accept()
print(f"Connection from {address} has been established.")
data = clientsocket.recv(2048)
print(data)
if data == b"open":
o = SqlServerRequest.dataForOpenOrders()
clientsocket.sendall(bytes(o,"utf-8"))
if data == b"closed":
c = SqlServerRequest.dataForClosedOrders()
clientsocket.sendall(bytes(c,"utf-8"))
clientsocket.close()
As context to my question, I am a computing student getting started with Python for the first time. Before this, I've worked mostly with Java and I am most comfortable with Java conventions and practices right now.
Background
An assignment for socket programming asks that we send strings between a server and client locally on the machine. We are provided sample (Python 2) code that instantiates a server and client. Outside of the context of the assignment, I wanted to create a version of this code that also runs in Python 3, but I was having problems getting the client to work the same in Python 3.
Changing server and client
Originally, the server required little changes and I was able to get it working. My code for the server is as follows:
#!/usr/bin/python3
import socket
HOST=''
PORT=5870
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.bind((HOST, PORT))
sock.listen(1)
conn, addr = sock.accept()
print('Connected by ', addr)
conn.sendto("Welcome to the server!", (HOST, PORT))
while True:
data = conn.recv(1024)
if not data: break
conn.sendall(data)
conn.close()
I'm not able to convert the client side to code that runs and functions within Python 3. I've tried digging deeper into the issue, but other online resources are not helpful for me (or at least, at my experience level). My server code is as follows.
#!/usr/bin/python3
import socket
HOST='127.0.0.1'
PORT=5870
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect((HOST, PORT))
data = sock.recv(1024)
print('Server sent', data)
sock.sendto("Hello world".encode(), (HOST, PORT))
data = sock.recv(1024)
print("Server sent", data)
sock.sendto("This is the second message".encode(), (HOST, PORT))
data = sock.recv(1024)
print('Server sent ', data)
sock.close()
The actual problem
Originally, this code for both the server and client used sendall() instead of sendto(), but I changed it after getting a TypeError in the client and reading this question. I'm still not exactly sure why this works or why I have to do this (although I would appreciate an explanation).
Now, when I run the client code, I'll get the same TypeError on the server even when I'm using sendto(), but I'm not sure how to resolve this problem in Python 3. The stacktrace I receive for the server as follows (I get a broken pipe on the client):
$ python3 mail_server.py
Connected by ('127.0.0.1', 41866)
Traceback (most recent call last):
File "mail_server.py", line 14, in <module>
conn.sendto("Welcome to the server!", (HOST, PORT))
TypeError: a bytes-like object is required, not 'str'
What am I doing wrong and how am I able to get this working in Python 3? Background context as to why this is would be especially helpful as I think part of my problem is that I'm not seeing why this change is necessary to begin with. Thanks!
Don't use sendto() on a stream socket. Once a socket is connected (and with stream sockets you can't do any data transfer until after connecting), you can't specify the destination, it's always sent to the remote address/port to which it's connected.
So use send() or sendall():
socket.sendall("Hello world".encode());
i recently started making a pure skype resolver and after doing everything fine i stuck on the socket communication.
Let me explain
I'm using python to get the user's IP and then the script opens a socket server and it sends the username to an other program written in .NET
Why is that? Well, the python skype API is not that powerfull so i'm using the axSkype library in order to gather more info.
The problem
The python socket sends the username as it should but i dont know the most efficient way to get the info back. I was thinking opening a socket server in the same script and wait for what the .NET program sends back.
I dont really kwon how to make this as fast as possible so i'm asking for your help.
The code
class api:
def GET(self, username):
skypeapi.activateSkype(username)
time.sleep(1) # because skype is ew
buf = []
print("==========================")
print("Resolving user " + username)
#This is where i'm starting the socket and sending data
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("127.0.0.1", 5756))
s.sendall(username)
s.close()
#at this poaint i want to get data back from the .NET app
for logfile in glob.glob('*.log'):
buf += logparse.search(logfile, username)
print("Done!")
print("==========================")
return json.dumps(buf)
class index:
def GET(self):
return render.index()
if __name__ == "__main__":
app.run()
You can bind your socket to the connection. This way, your socket stream will remain open and you will be able to send and receive information easily. Integrate this with the _thread module and you will be able to handle multiple streams. Here is some example code that binds a socket to a stream and just sends back whatever the clients sends it(Although in your case you could send whatever data is necessary)
import socket
from _thread import *
#clientHandle function will just receive and send stuff back to a specific client.
def clientHandle(stream):
stream.send(str.encode("Enter some stuff: "))
while True:
#Here is where the program waits for a response. The 4000 is a buffer limit.
data = stream.recv(4000)
if not data:
#If there is not data, exit the loop.
break
stream.senddall(str.encode(data + "\n"))
#Creating socket.
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
host = "" #In this case the host is the localhost but you can put your host
port = 80
try:
#Here the program tries to bind the socket to the stream.
s.bind((host, port))
except socket.error as e:
print("There was an error: " + str(e))
#Main program loop. Uses multithreading to handle multiple clients.
while True:
conn, addr = s.accept()
print("Connected to: " + addr[0] + ": " + str(addr[1]))
start_new_thread(clientHandle,(conn,))
Now in your case, you can integrate this into your api class(Is that where you want to integrate it? Correct me if I'm wrong.). So now when you define and bind your socket, use this code:
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((host, port))
Where, in your case, host is 127.0.0.1, in other words, your localhost, which can also be accessed by socket.gethostbyname(socket.gethostname())(but that's a bit verbose), and then port, which for you is 5756. Once you have bounded your socket, you have to accept connections through the following syntax:
conn, addr = s.accept()
Which then you can pass conn and addr to whatever function or just use in any other code.
Regardless of what you use it in, to receive data you can use socket.recv() and pass it a buffer limit. (Remember to decode whatever you receive.) And of course, you send data by using socket.sendall().
If you combine this with the _thread module, as shown above, you can handle multiple api requests, which could come handy in the future.
Hope this helps.
I'm currently working on with Sockets using Python.
As a starter, I tried copying first the examples given in this (17.2.2. Example) tutorial
I put the client and the server scripts in two different machines (of course)
Now, I want to try if it works, but I'm kind of lost.
I'm thinking of running the server program continuously so that it will keep on receiving the data sent by the client program. However, when I tried to run the Server program, it is giving me this error
socket.error: (99, 'Cannot assign requested address')
and When I tried running the client program, it doesnt give me errors, however, it is printing random data, which is different from what I'm expecting because I sent the String "Hello World", So im expecting that it will receive and print "Hello World"
Shown below is the server program
# Echo server program
import socket
HOST = '192.168.104.112' # Symbolic name meaning all available interfaces
PORT = 50007 # Arbitrary non-privileged port
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((HOST, PORT))
s.listen(1)
conn, addr = s.accept()
print 'Connected by', addr
while 1:
data = conn.recv(1024)
if not data: break
conn.sendall(data)
conn.close()
and the one below is the client program
# Echo client program
import socket
HOST = '192.168.104.111' # The remote host
PORT = 50007 # The same port as used by the server
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((HOST, PORT))
s.sendall('Hello, world')
data = s.recv(1024)
s.close()
print 'Received', repr(data)
Assuming that the IP of the machine that runs the server program is : 192.168.104.111
while the Client program is : 192.168.104.112
Im not really sure where to get the port number so I just used the port showed in the rpyc in the terminal. how do I get the correct port number anyway?
I know I made a lot of mistakes here. I just don't which part. Could you point me the mistakes that i've done and how to correct them? and how do I run these programs?
BTW, i'm using Centos.
On the server, HOST should be either 0.0.0.0 or the server's own IP address. The server needs to bind its listening port to its own interface(s). The client connects to the server.
Your client program doesn't check for errors. So if it can't connect to the server, things go awry.