Questions tagged [udp]

UDP stands for User Datagram Protocol. With UDP applications can send messages (datagrams) to other hosts on a network without requiring prior communications to set up special transmission channels or data paths.

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Debian udp port fowrding to another server does not work?

I have PC A (192.168.255.126, eth1) and it will receive some UDP packets, port: 51000. Now I wish the PC A will automatically forward the UDP packets to PC B (192.168.255.127) I have found many ...
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NGINX UDP Proxy Pass to HTTP

I built a NGINX reverse proxy where I listen for UDP traffic on port 53 and pass it on to an HTTP endpoint with modified headers. Once the headers are modified, I send the packet to the target. http....
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How 2 dynamic (external) IP devices can talk to each other via 1 static (external) IP [closed]

I have 3 devices: Device 1 (Dynamic IP): A raspberry Pi sending UDP packets to Device 2 via 4G modem via Internet Device 2 (Static IP): My Ubuntu/Windows PC with static IP, successfully receives ...
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Forwarding UDP traffic from one host to another

I have two hosts, each with 2 network interfaces: host1: eth0:172.16.125.5 eth1:172.165.8.55 host2: eth0:172.16.125.6 eth1:172.165.8.56 I want to forward all UDP traffic to host1:eth1 port 1234 to ...
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WCF Discovery on Windows Server 2019 getting ICMP Typ 3 Code 3

The problem: I've installed Windows Server 2019 and I am trying to discover my WCF services running on a Windows Server 2012R2. But that's not working and in Wireshark I see a ICMP Destination ...
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How can I send multicast UDP between 2 servers connected via cross-cable?

We have 2 servers (Centos 7) with Solarflare cards directly connected as 172.16.1.1 and 172.16.1.2. The servers also have other network interfaces. I'd like test sending UDP multicast packets from ...
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Are there STUN implementations that can sometimes handle symmetric NATs?

I've been working on connecting two devices that are each behind a symmetric NAT and managed to make it work quite consistently. However, it takes quite some time for the connection to happen (...
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How can I simulate UDP fragementation for network testing?

Is there a way to use iperf3—or another similar tool—to generate fragmented UDP packets? I suspect my firewall isn't reassembling them properly.
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huge difference in RX bytes vs TX bytes (ifconfig) on Syslog-NG server

we have a syslog-ng server acting as an intermediary logger. the server receives data from all devices on the network (from many different sources, on both UDP & TCP ports), filters them a bit, ...
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Fix UDP issues on subnet

I currently have a network with the following topography: topography Networking is fine and all works well, except for one thing: UDP seems to be unstable/not working on the subnets 192.168.3 and 192....
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Increased CPU interrupts, degraded performance on upgrade to Symfony flex

We're upgrading our Symfony 3.4 app (LAMP w/ opcache/php-fpm) to flex (as per https://symfony.com/doc/current/setup/flex.html). In load testing, we're seeing increased CPU usage, particularly system ...
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Forward incoming UDP Packets on Windows Server to client on different interface

I have the following setup with 2 networks and 3 clients: Network A: 192.168.0.0/16 Network B: 172.16.0.0/12 Client 1 is connected to Network A (192.168.0.1) Client 2 (Windows Server) is connected ...
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Video streaming via UDP on gigabit ethernet = packet lost

We are observing a strange behavior on a video streaming application over UDP on the same LAN. The sender send an H264 video via UDP through ethernet configured as 1000BaseT-FD, the receiver receive ...
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ncat script to test source IP addresses with UDP load balancer

I have two Ubuntu Virtual Machines behind an Azure Load Balancer. I'm observing some inconsistencies with the source IP addresses set in outgoing UDP packets from the VM's. I'm trying to come up with ...
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OpenVPN: UDP broadcast in tap environment

Background: I am currently trying to create a VPN for playing old computer games via LAN (Empire Earth / Warcraft III) and to bypass geo-blocks. I am using the docker image by kylemanna and my openvpn....
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upstream timed out (110: Connection timed out) while proxying connection - Nginx/Raspberry Pi/Ubuntu 20.04

I cannot find any help with UDP, so I have come here to ask. I have a DNS cluster set up on Raspberry Pis running Ubuntu 20.04 and Nginx. The proxy is used for UDP on port 53. I am needing to put this ...
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Enable GRO for UDP port explicitly

I am implementing a simple socket application in python and I need it to receive UDP packets with GRO enabled. I have checked that only the Python service is running and that GRO is enabled via ...
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Redirecting all outbound traffic to loopback for VPN program

I haven't been able to find much information on how a VPN would work from a programming perspective. I figured you'd have to reroute all packets from localhost to a local application, and therefrom ...
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sending Udp Datagram across different subnets behind router

I have a sample Windows computer network as shown in attached example network diagram. I want to send a simple udp packet from laptop 02 to laptop 04. I have also added manual static routes in the ...
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Possible to send real IP through Nginx UDP balancer to DNSMasq backend?

UPDATE: I uninstalled Nginx and reinstalled/compiled from source so I could get the ngx_stream_realip_module, but still cannot figure out how to forward the client IP instead of the proxy IP. I have ...
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How does the A record change over time by running a DNS query? [closed]

I am running a DNS query on www.wikipedia.org using Google's public resolver @8.8.8.8 using the mac terminal. I have to get the A records for the host and run the query a couple of times to notice any ...
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iptables udp port forwarded but ICMP UDP Port unreachable

I wish to host a game server (Zandronum Doom) on port 10666 UDP, but no one can connect to it. I have troubleshot the problem and I think it's a problem with my routing. My physical network ...
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Nginx: Unknown log format error

I have a proxy set up that is taking UDP traffic to load balance internal DNS. It is routing the traffic properly to my backend DNS servers, but I cannot seem to get the log formatting to work ...
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I have no access to router and portforward and i need to run a webserver [closed]

I got some PCs in some different locations with different ISPs and networks with dynamic ip addresses and I have a dynamic dns server that can records new IPs. but there is a problem. ISPs blocked all ...
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InfluxDB running on Debian 9 UDP is missing ip4 connection

I have an InfluxDB 1.8 running on a Debian Stretch server. I run a Python program against this server (from a Windows10 machine) and read/write data from/to Influx. For HTTP everything is fine, but as ...
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UDP NAT traffic but no response on MikroTik RouterOS

I have a MikroTik router with v7.1beta2 firmware installed It's WAN (eth1) has an IP address of 192.168.7.122 There are two devices connected to its LAN Device #1 is a webserver, communicating on ...
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iptables - perfect forwarding of port range to single port - p2p NAT traversal - how to keep the source UDP port untouched on the server?

To all the iptables gurus out there: I'm doing a little research on the viability of doing UDP hole punching to achieve NAT traversal in my network - I'm trying to figure out which UDP ports EXACTLY ...
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Traffic Control on Pritunl

I have a OVH-Game server with a 1Gbps Port and from time to time I will do speedtest. When the server is in mitigation and the download speed of the test goes over 30mbps you get disconnected for a ...
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What GCP product to use to run Docker container exposing a range of UDP ports to public internet

I am confused about which GCP product to use such that I can run a Docker container e.g. like "docker run -p 5001-5110:5001-5110/udp hunter_ctrl_standalone:latest -s foo". The container will ...
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Can a connection between “cone NAT with port restriction” and “symmetric NAT” be established without a third-party?

Directly it's impossible, right? Using an intermediate server isn’t an option because I have a requirement that says that a solution has to exchange lots of data and also be fast. Although, creating a ...
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Hyper-V VM's LocalPorts blocked

I am having issues with Local ports on hyper-V VM's I have enabled Hyper-V on my Windows10 laptop and Deployed windows 2019 sever Virtual machines to create the SCCM Lab environment. All Virtual ...
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1answer
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Docker cant resolve DNS-Names outside of docker network. Receiving “read from DNS server failed”

I have deployed an Adguard Home docker container which i want to use as my DNS server/proxy. DNS resolution is working fine when i'm making an nslookup from a machine (as well as the docker host) on ...
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UDP-Packets seem to get lost in IPsec tunnel from Strongswan to AWS cloud - connection works with Openswan

Use case: IOT-device connected through AWS cloud The IOT-device is behind a router that sends all traffic through aws cloud. The IOT-server can not be configured and thus is not part of the AWS cloud ...
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netsed not directing packets to remote server

I'm trying to spoof a packet that gets sent from a client process to port 8092 of a game server via UDP. I've tried to set up a transparent proxy via iptables like so: sudo iptables -t nat -A OUTPUT -...
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Forge UDP checksum

We're having some IPSec connection problems that seem connected to the UDP checksum beeing (incorrectly) set with some ISPs. To investigate further, I want to reproduce the error within a controlled ...
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146 views

OpenVPN does not connect outside network

We have a small office setup, currently due to pandemic employees need to work remotely therefore we are tying to configure OpenVPN so they can access internal applications. Using following tutorial I'...
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1answer
180 views

iptables: redirecting inbound UDP to a different port, and response going out the “public” port

I have an SNMP agent listening on a high-level port (16161) and I want to redirect traffic from the standard SNMP agent port 161. Easy iptables rule: iptables -t nat -A PREROUTING -p udp --dport 161 -...
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UDP connection i/o timeout while port is reachable

on one server we encountered an issue where all kinds of UDP connections are failing. The same application and tests work on other servers with the same OS and similar setup. nc -vz -u 83.61.**.** ...
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UDP NAT is not working

I have, among others, the following iptables NAT rules on the machine with IP addresses 192.168.1.71 and a.b.c.d, where a.b.c.d represents a public IP address: iptables -t nat -A PREROUTING -p udp --...
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How to check the udp port is accessible in an Ubuntu machine which is protected by a firewall

We were trying to install "Big blue button" in an Ubuntu server with a firewall. For installation, we need these UDP ports ("16384-32768") should be opened in the firewall. But we don't know whether ...
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1answer
257 views

Decoding TCP packets as RTP in Wireshark

I'm troubleshooting a WebRTC video calling problem in my app and i'm using Wireshark. One end of my video call is a web app running in my browser window and the other end is a Unity based app on an ...
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758 views

How to trace UDP blocking for DNS port 53

Recently both of our DNS servers stopped responding to incoming UDP on port 53, tested with dig and it works with TCP. They both have common ISP. Is there any way to traverse route and find out ...
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OpenVPN using UDP is terrible slow over cellular networks

I have a weird problem with OpenVPN for around two weeks now. I am running the OpenVPN server on a Virtual Server (German Hoster netcup) on UDP port 1194. Using this setup clients connecting through a ...
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how to proritize UDP port in tc

I have this TC code sudo tc qdisc add dev eth0 root handle 1: prio sudo tc filter add dev eth0 protocol ip parent 1: prio 1 u32 match ip dport xxxx 0xffff flowid 1:1 where XXXX is the port number. ...
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iptables: setting specific rules to IP aliases

We run several game servers all using one port with the use of IP Aliasing, the game servers bind to a specific aliased IP that belongs to the main dedicated server. I've setup netplan already and it ...
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Find the process listening on a port (not showing in lsof)

Using Ubuntu 18.04 I want to know which process or kernel function listens on UDP port 38637. I have researched this problem and found similar questions: https://superuser.com/questions/42843/...
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OVH server DDOS attack protection

I purchased the server on ovh.com. (not gaming, regular) For 3 days now I’ve been trying to set up protection against DDOS flood. Nothing comes out. Support responds once a day and does not give an ...
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464 views

How to capture UDP traffic so it can be piped to grep

I'm trying to capture UDP traffic which is being sent as StatsD metrics (on port 8125). The most simple approach I tried is to run nc -ul 8125 which prints the metrics to the terminal...but they are ...
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How does TCP over UDP get return packets

How does a server send packets back to the client if there is only a UDP connection, when the client is behind a firewall, and UDP by definition does not maintain a stateful connection. If I had a ...
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UDP comunication at the and of a TCP request

I'm learning about network protocols, in particular TCP and UDP. I've written a c++ client that get the HTTPS response of this page 216.58.198.35 (Google), then I've used Wireshark to analyze the ...

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