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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.

Because UDP doesn't rely on handshaking to guarantee that packets arrive and in order it can be seen as an unreliable protocol, but for real time systems where acting on the data immediately is the most important consideration not having to wait for delayed packets is a distinct advantage.

UDP is just one communications protocol on the web. Others include:

  • Transmission Control Protocol (TCP)
  • Internet Control Message Protocol (ICMP)
  • Hypertext Transfer Protocol (HTTP)
  • Post Office Protocol (POP3)
  • File Transfer Protocol (FTP)
  • Internet Message Access Protocol (IMAP)

UDP on Wikipedia

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What is the difference between bind, network (interface) and multicast addresses?

The DatagramSocketImpl in Java has a joinGroup method that takes a socket address (IP and PORT) plus the interface address (IP and PORT). I am trying to understand the difference and purpose of each of those three addresses in the multicast…
chrisapotek
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tcpdump udp data capture latency

I am using tcpdump to capture UDP packets and analyze network latency between a UDP broadcaster and my server. To calculate latency I compare the source host timestamps reported in UDP application data to the tcpdump local "kernel" timestamps. The…
Robert Kubrick
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Service to temporarily queue UDP packets

I have a service running on a linux box that receives a fairly constant stream of packets via UDP. The occasional loss or corruption of packets associated with using UDP is fine. However, the service is under active development, and gets updated…
mikeocool
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Finding the executable sending packets to a specific IP Address?

We host Game Servers off of Windows Server 2008 machines, and we just received a report that one of our customers is using their server to do some type of UDP attack. The person being attacked provided us with the IP address, but do to IPv4…
Aidan Knight
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NetBIOS over TCP/IP with no UDP

Is there a way to run NetBIOS entirely on TCP? I have an environment where UDP is not allowed. I need a way for the machines to talk to each other by name. I thought there might be a way to say that NetBIOS should run only on TCP and not on UDP. Is…
Martin
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Port Knocking and TCP/IP within the OSI model

I have read that Port Knocking can be subject to false negative (type II error) due to the optimization techniques of TCP/IP. A correct port knock given by the client may be read as incorrect by the server. Is this avoidable by using only UDP and/or…
jtrip
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one particular laptop does not receive UDP broadcast messages

I am trying to debug a problem with a particular laptop which is running Ubuntu. We have a service which uses broadcast UDP messages, and this laptop is not receiving them on its wireless interface, except occasionally. I have boiled the problem…
Steve
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Multicast IP Addresses

I posted this on StackOverflow and was told it might be more appropriate here. I'm having trouble understanding how multicast addresses work. First off, is it true that if I have N clients or peers working on separate networks, they all subscribe to…
Josh G
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udp through nat

I've two private networks (each of them behind a typical dsl router). The routers are connected to the WWW. The extern interface of each router have one dynamic IP address. I want to stream data via UDP directly between one client in private network…
youllknow
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netstat reports UDP ports with no owning process

When I run netstat -avp udp I get a slowly growing number of ports. It grows about 100 an hour but the rate varies considerably. When I close the process, the ports do not disappear from the list. Similarly when I kill the process. Restarting the…
Simon G.
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nginx config for reverse proxying UDP traffic (minecraft app) - 90 message too long

Trying to proxy udp traffic. nginx doesn't throw any error about the configuration. The client connects until half-way (it says it could reach the end server) but the connection then gets stuck and eventually closes out with timeout. nginx version:…
seb
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How can I make my libvirt/KVM guest see all IPv4/UDP multicast traffic?

I have an issue with IPv4/UDP multicast traffic not being fully visible from within a KVM guest. The guest has a dedicated NIC which is attached using MacVTap. Both the host OS and the OS in the guest are Ubuntu 18.04. This is the VM’s network…
aaronk6
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Cloning a UDP packet recieved on localhost to another IP

I have a machine A with local ip 192.168.0.199 - I want to clone all udp packets recieved on a local machine and forward to machine A i tried the below in IP tables sudo iptables -A OUTPUT -t nat -p udp -s 127.0.0.1 --dport 32000 -j TEE --gateway…
Jayaram
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How do I trigger a client reconnect with OpenVPN?

I am running multiple replicas of OpenVPN server (on a Kubernetes cluster) and have configured clients to reconnect should a server instance go down (with keepalive 10 60) which works fairly well. However, I was wondering if there is a way to…
dippynark
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Partially obstructed communication when publishing Docker container on different host port

I have a game server running inside a Docker container that listens on UDP port 1111 (EXPOSE 1111/udp). When I publish this server on the same port on the host (-p 1111:1111/udp) everything works as expected. Symptoms When I publish it on a…
Thomas
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