I want to broadcast a message among four raspberry Pis . I programmed the code By socket programming in python with UDP protocol . In order to send the message I used the broadcast IP address (192.168.0.255) and I test that in terminal on my computer it is work , but when I execute the same code on the Pi it is not working and no message is sent . When I send a message between two Pis and use (IP + port) it is work and the message is sent .
Did any one know what I must to change in my code ?? or in my Pi?? How I can broadcast this message ??
I also use the instruction (('', UDP_PORT)) and not work on Pi.
#Client.py
import socket
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM )
sock.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
UDP_IP = "192.168.0.255"
UDP_PORT = 50000
MSG = 'Hello, World!'
MESSAGE = str.encode(MSG)
print (("message:"), MSG )
sock.sendto(MESSAGE, (UDP_IP, UDP_PORT))
sock.close()
#server.py
import socket
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
UDP_IP = "192.168.0.101"
UDP_PORT = 5005
s.bind((UDP_IP, UDP_PORT))
print('socket is created')
while True:
data ,addr = s.recvfrom(1024)
print (('received message:') , data.decode("utf-8"))
Related
I'm trying to implement simple DHCP client. The problem is receiving UDP broadcast packets on network interface that hasn't assigned ip address yet.
I think I can simplify my issue to following scripts that I execute in docker containers working in the same bridge network.
sender.py:
import socket
UDP_IP = "255.255.255.255"
UDP_PORT = 5005
MESSAGE = b"Hello, World!"
print("UDP target IP: %s" % UDP_IP)
print("UDP target port: %s" % UDP_PORT)
print("message: %s" % MESSAGE)
sock = socket.socket(socket.AF_INET, # Internet
socket.SOCK_DGRAM) # UDP
sock.setsockopt(socket.SOL_SOCKET, 25, str(f"eth1" + '\0').encode('utf-8'))
sock.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
sock.sendto(MESSAGE, (UDP_IP, UDP_PORT))
receiver.py:
import socket
UDP_IP = ""
UDP_PORT = 5005
sock = socket.socket(socket.AF_INET, # Internet
socket.SOCK_DGRAM) # UDP
sock.bind((UDP_IP, UDP_PORT))
sock.setsockopt(socket.SOL_SOCKET, 25, str(f"eth1" + '\0').encode('utf-8'))
while True:
data, addr = sock.recvfrom(1024)
print("received message: %s" % data)
If i execute upper scripts when ip address is statically assigned to eth1- interface (172.1.2.2) i receive packet. But after deleting ip address:
ip addr del 172.1.2.2/24 dev eth1
I can't receive anything.
Of course i can observe sent packet on eth1 on receiver side by tcpdump.
How can i receive UDP broadcast packet, on interface that doesn't have assigned ip address ?
Good morning. I have recently started learning network and Python programming with using Raspberry Pi (emulator program on Linux) and i have a little problem. My homework is make server and three clients where this clients should get information about temperature from raspberry through server (server sends temperature) in same time (important!) but as I can see this clients get information but it is looks like 1 client get and rest wait until he receive temperature....and I really don't know what change should I make in my code : (
serwer.py
from sense_emu import SenseHat
from time import sleep
import socket
sense = SenseHat()
UDP_IP = "127.0.0.1"
UDP_PORT = 5005
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
while 1:
temp = sense.temp
tempe = str(temp)
message = tempe.encode('utf-8')
sock.sendto(message, (UDP_IP, UDP_PORT))
sleep(1)
client.py
from time import sleep
import socket
UDP_IP = "127.0.0.1"
UDP_PORT = 5005
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sock.bind((UDP_IP, UDP_PORT))
while 1:
message, addr = sock.recvfrom(1024)
mes = str(message)
print("received message:"+mes)
sock.close()
sleep(2)
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sock.bind((UDP_IP, UDP_PORT))
I really thought that it should works by bind socket on each client but unfortunately not.
you seem to be misunderstanding how sockets work, I'd suggest going doing some more reading about them
some pointers and general conventions:
normally the "server" process binds to a specific "well-known" port and clients connect to that address/port
UDP is unreliable (importantly in this case packets can get lost) hence you might need a way of retransmitting values
hosts are unreliable (e.g. they might be turned off, or change IP address), you might need some way of ensuring the server doesn't send too much data to hosts that might not exist
So, I have this code here. This sender script give's me the output properly.
import socket
UDP_IP = "127.0.0.1"
UDP_PORT = 0
MESSAGE = "Hi, can you listen to this?"
print "UDP target IP:", UDP_IP
print "UDP target port:", UDP_PORT
print "message:", MESSAGE
sock = socket.socket(socket.AF_INET, # Internet
socket.SOCK_DGRAM) # UDP
sock.sendto(MESSAGE, (UDP_IP, UDP_PORT))
I tried to use this script on another host and try to establish a communication between the two. (Both the systems are on the same network ex. 00.000.00.xxx , only the xxx part varies)
import socket
UDP_IP = "127.0.0.1"
UDP_PORT = 0
sock = socket.socket(socket.AF_INET, # Internet
socket.SOCK_DGRAM) # UDP
sock.bind((UDP_IP, UDP_PORT))
while True:
data, addr = sock.recvfrom(1024) # buffer size is 1024 bytes
print "received message:", data
Here is the output
Traceback (most recent call last):
File "C:/Users/bshivaku/Desktop/SEnd_Udp_packets.py", line 9, in <module>
sock.bind((UDP_IP, UDP_PORT))
File "C:\Python27\Lib\socket.py", line 228, in meth
return getattr(self._sock,name)(*args)
socket.error: [Errno 10049] The requested address is not valid in its context
I used the ip address of the receiver on the sender script and sender ip address on receiver
I am sure I made a mistake with the UDP_PORT so i used PORT= 0 and tried. How to request for port number? How do I establish the connection? If not the port, where am I going wrong?
When sending a message use a specific port, for example UDP_PORT=8765, otherwise if UDP_PORT is set to 0 then the system will chose a random port for you.
Use the ip address of the receiver host in the sender script and bind to any interface on the receiver script.
On the receiving side use the same UDP port number configured in the sender script.
receiver:
import socket
UDP_IP = "0.0.0.0"
UDP_PORT = 8543
sock = socket.socket(socket.AF_INET, # Internet
socket.SOCK_DGRAM) # UDP
sock.bind((UDP_IP, UDP_PORT))
while True:
data, addr = sock.recvfrom(1024) # buffer size is 1024 bytes
print "received message:", data
sender:
import socket
UDP_IP = "<ip_address_of_receiver>"
UDP_PORT = 8543
MESSAGE = "Hi, can you listen to this?"
print "UDP target IP:", UDP_IP
print "UDP target port:", UDP_PORT
print "message:", MESSAGE
sock = socket.socket(socket.AF_INET, # Internet
socket.SOCK_DGRAM) # UDP
sock.sendto(MESSAGE, (UDP_IP, UDP_PORT))
Aside the UDP addresses setting there are not any problems on python side.
About the error:
[Errno 10049] The requested address is not valid in its context
This normally stems from an attempt to bind to an address that is not valid for the local computer: so it seems that the loopback address 127.0.0.1 it is not configured on your machine.
Investigate on the sys admin side, for example check if the IPv4 network stack is enabled on your machine.
Here is broadcast server
from time import sleep
from socket import *
PORT = 50000
s = socket(AF_INET, SOCK_DGRAM)
s.bind(('', 0))
s.setsockopt(SOL_SOCKET, SO_BROADCAST, 1)
data = "I am server"
while 1:
s.sendto(data, ('<broadcast>', PORT))
print "sent data"
sleep(5)
Please note that you need to change '<broadcast>' with actual broadcast address of your network. Please see Python can't send a broadcast package with address
Here is broadcast receiver
from socket import socket, AF_INET, SOCK_DGRAM
PORT = 50000
client = socket(AF_INET, SOCK_DGRAM)
client.bind(('0.0.0.0', PORT))
data, addr = s.recvfrom(1024) #sticks here forever!
if data:
print "Found Broadcast server at : " + addr
But problem is that my receiver just sticks at s.recvfrom(1024)
While through tcpdump I am able to see the packet, then why this python client is not able to catch it ?
command is sudo tcpdump -i wlan0 ip -X dst host 255.255.255.255
I changed your code to Python 3 and corrected 2 errors:
Change s to client
Print the statement only when there is data from recvfrom()
Hope it helps.
from socket import socket, AF_INET, SOCK_DGRAM
PORT = 50000
client = socket(AF_INET, SOCK_DGRAM)
client.bind(('0.0.0.0', PORT))
while True:
data, addr = client.recvfrom(1024) #sticks here forever!
if data:
print("Found Broadcast server at : ", addr)
You need to set socket options before you bind it, and you need to bind it to INADDR_BROADCAST.
I am able to send and receive UDP messages in separate programs, but I'm not able to do the same task in one program.
import socket
UDP_IP = "192.168.1.178"
UDP_PORT = 8888
msg = 'test'
print "UDP target IP: ", UDP_IP
print "UDP target PORT: ", UDP_PORT
print "Message: ", msg
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.sendto(msg, (UDP_IP, UDP_PORT))
UDP_IP2 = "192.168.1.198"
sock.bind((UDP_IP2, UDP_PORT))
while True:
data, addr = sock.recvfrom(1024) # buffer size is 1024 bytes
print "received message:", data
With this program, I am able to send UDP messages, however, I am not able to receive any messages from the other machine.
What am I doing wrong?
Thanks in advance,
Mikkel
In your example you try to bind socket addr after sending, what's wrong.
Address can be bound to socket only before any data transfer.
If there is no explicit bind OS sets any free (unused) port number in range [1024, 65535] on first .send()/.recv() call.
Next, socket can be bound only to single IP (except special case '0.0.0.0' which means "all host's interfaces").