I have a pair of Python scripts that communicate through UDP. The scripts work fine as-is if they are both on Windows computers.
The idea is to send data from 10.10.10.56 on a Windows machine to 10.10.10.40 on a Ubuntu one. The communication is through a WiFi router, on a static ipv4 profile.
The Python codes are as seen below:
##Server
import socket
import struct
import time
remoteIP = "10.10.10.40"
port = 8080
bufferSize = 1024
# Create a datagram socket
UDPServerSocket = socket.socket(family=socket.AF_INET, type=socket.SOCK_DGRAM)
message1 = [0]*(62501)
cnt = 0
while(True):
time.sleep(1/30)
cnt = 1
if cnt == 255:
cnt = 0
message1[0] = cnt
_bytes_to_send = struct.pack("B"*len(message1), *message1)
UDPServerSocket.sendto(_bytes_to_send, (remoteIP,port))
##Client
#!/usr/bin/env python
import socket
import struct
serverAddressPort = ("0.0.0.0", 8080)
bufferSize = 1024
# Create a UDP socket at client side
sock = socket.socket(family=socket.AF_INET, type=socket.SOCK_DGRAM)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR,1)
sock.bind(serverAddressPort)
while True:
print("Looping!")
msgFromServer = sock.recvfrom(1024)[0]
print(msgFromServer)
mx = [int(x) for x in msgFromServer]
print(mx)
print("----------------------------")
The troubleshooting steps I've taken so far:
- Check Wireshark for incoming UDP packets from
10.10.10.56. It indeed does confirm that there are UDP packets inbound to the receiving side. - Check that the network profiles are assigned properly on
nmcli. I can post any terminal output necessary for debugging purposes related to my network profiles. - Use a specific IP address (
10.10.10.56) on the receiving side instead of using"". Results in:
Traceback (most recent call last):
File "udp_client.py", line 14, in <module>
sock.bind(serverAddressPort)
OSError: [Errno 99] Cannot assign requested address
- Using the exact same scripts on a Windows install for the listener
10.10.10.40to communicate with the sender Windows machine10.10.10.56(works), also make the sender10.10.10.56a Ubuntu machine (doesn't work). - Check the firewall settings with
ufw. It is inactive.
I am afraid that this might be related to my network settings, but I have done exactly whatever I have done on the Windows side of things with Ubuntu. I don't simply understand what could be wrong considering that this does indeed work on Windows.
Finally, here's my nmcli c show output for the WiFi profile:
connection.id: ASUS_88
connection.uuid: ff935490-4b0f-447f-b303-276c5c1ed104
connection.stable-id: --
connection.type: 802-11-wireless
connection.interface-name: wlp5s0
connection.autoconnect: yes
connection.autoconnect-priority: 0
connection.autoconnect-retries: -1 (default)
connection.multi-connect: 0 (default)
connection.auth-retries: -1
connection.timestamp: 1659449375
connection.read-only: no
connection.permissions: --
connection.zone: --
connection.master: --
connection.slave-type: --
connection.autoconnect-slaves: -1 (default)
connection.secondaries: --
connection.gateway-ping-timeout: 0
connection.metered: unknown
connection.lldp: default
connection.mdns: -1 (default)
connection.llmnr: -1 (default)
connection.wait-device-timeout: -1
802-11-wireless.ssid: ASUS_88
802-11-wireless.mode: infrastructure
802-11-wireless.band: --
802-11-wireless.channel: 0
802-11-wireless.bssid: --
802-11-wireless.rate: 0
802-11-wireless.tx-power: 0
802-11-wireless.mac-address: --
802-11-wireless.cloned-mac-address: --
802-11-wireless.generate-mac-address-mask:--
802-11-wireless.mac-address-blacklist: --
802-11-wireless.mac-address-randomization:default
802-11-wireless.mtu: auto
802-11-wireless.seen-bssids: 04:D4:C4:34:A4:88
802-11-wireless.hidden: no
802-11-wireless.powersave: 0 (default)
802-11-wireless.wake-on-wlan: 0x1 (default)
802-11-wireless-security.key-mgmt: wpa-psk
802-11-wireless-security.wep-tx-keyidx: 0
802-11-wireless-security.auth-alg: --
802-11-wireless-security.proto: --
802-11-wireless-security.pairwise: --
802-11-wireless-security.group: --
802-11-wireless-security.pmf: 0 (default)
802-11-wireless-security.leap-username: --
802-11-wireless-security.wep-key0: <hidden>
802-11-wireless-security.wep-key1: <hidden>
802-11-wireless-security.wep-key2: <hidden>
802-11-wireless-security.wep-key3: <hidden>
802-11-wireless-security.wep-key-flags: 0 (none)
802-11-wireless-security.wep-key-type: unknown
802-11-wireless-security.psk: <hidden>
802-11-wireless-security.psk-flags: 0 (none)
802-11-wireless-security.leap-password: <hidden>
802-11-wireless-security.leap-password-flags:0 (none)
802-11-wireless-security.wps-method: 0x0 (default)
802-11-wireless-security.fils: 0 (default)
ipv4.method: manual
ipv4.dns: --
ipv4.dns-search: --
ipv4.dns-options: --
ipv4.dns-priority: 0
ipv4.addresses: 10.10.10.40/24
ipv4.gateway: 255.0.0.0
ipv4.routes: --
ipv4.route-metric: -1
ipv4.route-table: 0 (unspec)
ipv4.routing-rules: --
ipv4.ignore-auto-routes: no
ipv4.ignore-auto-dns: yes
ipv4.dhcp-client-id: --
ipv4.dhcp-iaid: --
ipv4.dhcp-timeout: 0 (default)
ipv4.dhcp-send-hostname: yes
ipv4.dhcp-hostname: --
ipv4.dhcp-fqdn: --
ipv4.dhcp-hostname-flags: 0x0 (none)
ipv4.never-default: no
ipv4.may-fail: yes
ipv4.dad-timeout: -1 (default)
ipv6.method: auto
ipv6.dns: --
ipv6.dns-search: --
ipv6.dns-options: --
ipv6.dns-priority: 0
ipv6.addresses: --
ipv6.gateway: --
ipv6.routes: --
ipv6.route-metric: -1
ipv6.route-table: 0 (unspec)
ipv6.routing-rules: --
ipv6.ignore-auto-routes: no
ipv6.ignore-auto-dns: no
ipv6.never-default: no
ipv6.may-fail: yes
ipv6.ip6-privacy: -1 (unknown)
ipv6.addr-gen-mode: stable-privacy
ipv6.ra-timeout: 0 (default)
ipv6.dhcp-duid: --
ipv6.dhcp-iaid: --
ipv6.dhcp-timeout: 0 (default)
ipv6.dhcp-send-hostname: yes
ipv6.dhcp-hostname: --
ipv6.dhcp-hostname-flags: 0x0 (none)
ipv6.token: --
proxy.method: none
proxy.browser-only: no
proxy.pac-url: --
proxy.pac-script: --
iptables -L output:
Chain INPUT (policy ACCEPT)
target prot opt source destination
ACCEPT all -- anywhere anywhere ctstate RELATED,ESTABLISHED,DNAT
ACCEPT all -- anywhere anywhere
INPUT_direct all -- anywhere anywhere
INPUT_ZONES all -- anywhere anywhere
DROP all -- anywhere anywhere ctstate INVALID
REJECT all -- anywhere anywhere reject-with icmp-host-prohibited
Chain FORWARD (policy ACCEPT)
target prot opt source destination
ACCEPT all -- anywhere anywhere ctstate RELATED,ESTABLISHED,DNAT
ACCEPT all -- anywhere anywhere
FORWARD_direct all -- anywhere anywhere
FORWARD_IN_ZONES all -- anywhere anywhere
FORWARD_OUT_ZONES all -- anywhere anywhere
DROP all -- anywhere anywhere ctstate INVALID
REJECT all -- anywhere anywhere reject-with icmp-host-prohibited
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
ACCEPT all -- anywhere anywhere
OUTPUT_direct all -- anywhere anywhere
Chain FORWARD_IN_ZONES (1 references)
target prot opt source destination
FWDI_public all -- 52.209.204.108 anywhere [goto]
FWDI_public all -- anywhere anywhere [goto]
FWDI_public all -- anywhere anywhere [goto]
Chain FORWARD_OUT_ZONES (1 references)
target prot opt source destination
FWDO_public all -- anywhere 52.209.204.108 [goto]
FWDO_public all -- anywhere anywhere [goto]
FWDO_public all -- anywhere anywhere [goto]
Chain FORWARD_direct (1 references)
target prot opt source destination
Chain FWDI_public (3 references)
target prot opt source destination
FWDI_public_pre all -- anywhere anywhere
FWDI_public_log all -- anywhere anywhere
FWDI_public_deny all -- anywhere anywhere
FWDI_public_allow all -- anywhere anywhere
FWDI_public_post all -- anywhere anywhere
ACCEPT icmp -- anywhere anywhere
Chain FWDI_public_allow (1 references)
target prot opt source destination
Chain FWDI_public_deny (1 references)
target prot opt source destination
Chain FWDI_public_log (1 references)
target prot opt source destination
Chain FWDI_public_post (1 references)
target prot opt source destination
Chain FWDI_public_pre (1 references)
target prot opt source destination
Chain FWDO_public (3 references)
target prot opt source destination
FWDO_public_pre all -- anywhere anywhere
FWDO_public_log all -- anywhere anywhere
FWDO_public_deny all -- anywhere anywhere
FWDO_public_allow all -- anywhere anywhere
FWDO_public_post all -- anywhere anywhere
Chain FWDO_public_allow (1 references)
target prot opt source destination
Chain FWDO_public_deny (1 references)
target prot opt source destination
Chain FWDO_public_log (1 references)
target prot opt source destination
Chain FWDO_public_post (1 references)
target prot opt source destination
Chain FWDO_public_pre (1 references)
target prot opt source destination
Chain INPUT_ZONES (1 references)
target prot opt source destination
IN_public all -- 52.209.204.108 anywhere [goto]
IN_public all -- anywhere anywhere [goto]
IN_public all -- anywhere anywhere [goto]
Chain INPUT_direct (1 references)
target prot opt source destination
Chain IN_public (3 references)
target prot opt source destination
IN_public_pre all -- anywhere anywhere
IN_public_log all -- anywhere anywhere
IN_public_deny all -- anywhere anywhere
IN_public_allow all -- anywhere anywhere
IN_public_post all -- anywhere anywhere
ACCEPT icmp -- anywhere anywhere
Chain IN_public_allow (1 references)
target prot opt source destination
ACCEPT tcp -- anywhere anywhere tcp dpt:ssh ctstate NEW,UNTRACKED
Chain IN_public_deny (1 references)
target prot opt source destination
Chain IN_public_log (1 references)
target prot opt source destination
Chain IN_public_post (1 references)
target prot opt source destination
Chain IN_public_pre (1 references)
target prot opt source destination
Chain OUTPUT_direct (1 references)
target prot opt source destination
Thanks in advance.
CodePudding user response：
It appears that this problem is related to firewall settings even though ufw and iptables were of no help in particular.
Turning off the firewall through systemctl by
sudo systemctl stop firewalld
seems to solve the issue for Ubuntu 20.04. Hope this helps other people facing this issue.