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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Route only on output chain?

I have two machines A and B. I want to send iperf traffic from A to B, but first have it route through a userspace program on A. I did this with a tunneling device: therefore, I used the command ip ...
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iptables block access to all ports except 53 (tcp,udp) from one IP address

how can i block all ports from one IP address except the port 53 TCP,UDP? example: ip 192.168.0.15 access only port 53 (udp,tcp). thank you.
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14 views

How to tunnel UDP traffic over Tor?

I know that Tor does not support UDP for now . But I came upon certain application Onion Cat .But I don't know if it work or not . Is there any other procedure ? Is that even possible ? Please guide ...
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90 views

ISP Issues - TCP Out-of-Order

Accessing any webpage (basically any TCP connection), results in multiple retries before and long loading times before it loads a page with missing elements (reload might fix it). Google Chrome throws ...
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3answers
293 views

Is it possible to process millions of datagrams per second with Windows?

I am investigating if I can implement an HPC app on Windows that receives small UDP multicast datagrams (mostly 100-400 Bytes) at a high rate, using a dozen or up to maybe 200 multicast groups (i.e. ...
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20 views

UDP over Internet

I have a small problem: I want to program a simple Apllication that sends a small word (in this case: "Hello") to a server. This Server should display it via cout. This is just a project to learn how ...
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55 views

UDP traffic through OpenVPN tunnel

I want to tunnel UDP traffic (Video) through OpenVPN between two clients. I am able to ping both the clients but unable to transmit video through the tunnel to the Client B.
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34 views

Can't connect to udp tracker (Rtorrent)

So I just got rtorrent, fixed my settings, but it still won't connect to udp no matter which torrent i use, udp is enabled and every settings seems fine. Still I can't connect! Reply if you need some ...
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1answer
22 views

Unable to see broadcast packets with tcpdump

I am launching an application which broadcasts udp packets. I also have a simple python script to confirm that these packets are being broadcast: sock = socket.socket(socket.AF_INET, ...
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37 views

UDP traceroute delay?

We are seeing timeout packages when running traceroute command between two Linux systems on a private network. However, we do not see such symptoms using TCP or ICMP over traceroute. This is a private ...
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47 views

sshuttle using tproxy error requires recvmsg function

I'm using sshuttle from this repo https://github.com/seanzxx/sshuttle because im using OSX Yosemite. (Original version from apenwarr not working with OSX Yosemite). it's working fine with this ...
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1answer
93 views

Why filtering on udp port in TCPDUMP gives only fragmented IP frames

I've a device capturing traffic with Tcpdump filtering on "upd dst port" then it creates a pcap file to be read in wireshark. what I obtain from running: tcpdump udp dst port 5201 -qUns 0 -i wlan0 ...
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35 views

What is the primary function of the transport layer in the Internet protocol networking code [closed]

I am not sure if I have answered this question right, so would appreciate it if someone could correct me. The question is: What is the primary function of the transport layer in the Internet protocol ...
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110 views

COD4 Linux game server doesn't send UDP packets as response to broadcast

I am setting up a bunch of Game servers for a medium sized LAN tournament using CentOS 6 and the various Linux binaries used for the game servers. With COD4 the servers did not show up in the server ...
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52 views

Forward all TCP and UDP connections over VPN

I have the following setup: OS: Ubuntu v13 Software: PPTP NIC 1 (eth1) IP: 10.2.95.207/24 Gateway: 10.2.95.1 (this is the network I want to connect to) NIC 2 (eth2) IP: 7.82.176.254/8 (the network ...
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27 views

Do I need to join a multicast group to send a packet or joining is just for listening?

I am confused here. Can anyone just send a packet to a multicast address and port? Where does the multicast group come into play here? Do I also need to send to a group? Can someone explain that to ...
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2answers
377 views

Testing a Firewall against outgoing UDP ports

I'm trying to test which outgoing ports are allowed through a firewall. At the moment I can do this for TCP by port scanning portquiz.net (which is a server with all TCP ports open) from inside ...
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1answer
121 views

utorrent connectivity: Router drops packets

I have some problems downloading via uTorrent 3.4.2 on Win 7 x64. Symptoms: DHT is either Waiting to log in or Nodes (0), under Trackers its status is Waiting for announce... For any torrent, all ...
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59 views

OpenVPN sans port forwarding on unfriendly networks

I have a problem. I'm about to move onto campus right in the middle of the semester. For a student, I have a complicated network setup where all of my systems are reliant on NAS and all of them VPN ...
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56 views

Home router config to allow for UDP broadcast

I have a homegrown piece of software that "listens" to UDP traffic at 255.255.255.255:5010. It works just great on my home network, but does not work on other people's networks. I think that my ...
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39 views

How to create a wireless-to-ethernet router?

I have a Debian machine, which I want to turn into a router. It will connect via wireless to a access-point, where it will get an IP. To its ethernet port, other machines will be connected. It will ...
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2answers
168 views

UDP socket flushed. What are the limitations? When it blocks?

I plan to send high amount of data through UDP (video streaming), and I thought in a system that requires to detect when an interface has reached maximum upload bandwith. I know that when I flush the ...
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1answer
2k views

Play UDP stream in VLC?

I receive an UDP video stream of which I know both the IP adresses and the incoming and outgoing ports of both computers. How can I plat his in vlc? udp:@:1234 Doesnt work for me. How to fix this?
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1answer
140 views

How to experience UDP hole punching using Ncat under Linux?

I'd like to see UDP hole punching in action. I tested it under Linux, using Ncat. Here's what I tried: Open port 1234/UDP on host A and port 12345/UDP on host B's firewall (I'm still behind NAT, but ...
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1answer
269 views

What is the difference between UDP and HTTP torrent trackers?

In the context of bittorrent what's the difference between http and udp trackers? HTTP is an application layer protocol and UDP is a transport layer protocol so the concepts seem non-overlapping. I ...
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1answer
169 views

Tunnelling UDP Traffic Through OpenVPN

Referring to this answer I'm trying to route UDP streaming through an available OpenVPN tunnel. On the VPN client machine, I've access to a UDP stream over an IP (udp://1.2.3.4:5555) which I want to ...
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1answer
130 views

Emulate console by sending data on one UDP port, and receive text from another

I'm trying to establish a “console-like” connection with a National Instruments cRIO-FRC. It broadcasts its console output onto 255.255.255.255, UDP port 6666. I can listen to it with: socat ...
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1answer
19 views

Which criteria is used by the linux kernel to pick udp source ports?

They are all of course greater than 1024, but can we narrow this range a bit more? Via wireshark the lowest I've seen is 30XXX. Does the kernel specify it's criteria somewhere?
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316 views

Can a VMWare player virtual machine receive udp packages?

I have a virtual machine running in VMWare player v6. The network type is NAT. An application in my virtual machine sends UDP packages to a server in the network of the host machine and needs to ...
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1answer
108 views

WPA blocks UDP broadcast

I use a convenient program called KDE Connect to interface a Linux/KDE computer with an Android device. It uses UDP broadcast. And it worked fine when my wifi was not encrypted. I recently had to ...
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1answer
83 views

UDP port scanning

UDP is connectionless, so I can't expect a response packet, necessarily. If the port is closed, I might get an ICMP error message, but if the firewall could silently drop the ICMP packet How could I ...
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1answer
40 views

VNC (or RDP) server using outbound connection only

How do I set up a VNC server that connects to an intermediary server to start an outbound communication, that can be used by a VNC client. This way the port forwarding doesn't need to be set up, and ...
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248 views

Re-stream (forward) UDP-Live-Video-Stream (using winsock) reduce video quality?

So, I used ffmpeg to stream the live webcam using UDP protocol to port 1111 : ffmpeg -f dshow -i video="Lenovo EasyCamera" -f mpegts udp://localhost:1111 When I played it directly by ffplay from ...
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2answers
153 views

Is the Transport Layer (e.g. UDP, TCP) handled by the Operating System usually? [closed]

I'm really new to networking and am struggling to understand this. I know the Transport Layer in the Internet Protocol Suite (at least the UDP and TCP protocols) contains the source and destination ...
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1answer
36 views

NAT and UDP replies by default

If I send UDP packets from Machine A with local port M behind a NAT to Machine B's port N, where Machine B is outside the NAT (elsewhere on the Internet), can I reasonably expect that NAT would pass ...
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2answers
257 views

What does a network packet consists of?

I know basic networking but I am not very good at it. Now I am calculating how many packets will be lost if I use UDP over IPv4. I can assume that the protocol overhead for data sent via UDP over IPv4 ...
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1answer
72 views

14 bytes preceeding the UDP packet, what is their purpose? Linux

I am analysing packets being sent from an MT4000 telemetry device. I have set up a listener in the terminal(Linux) and set to display the packets being received in hex. So far the packet incoming ...
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348 views

Streaming screen over LAN with VLC using RTP

I am trying to stream the screen (video and audio) from a Windows PC to a Linux one (Raspberry Pi), using VLC. I have tried emitting the screen through RTP (I want to do unicast), and then in the ...
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897 views

udp client sending ICMP “port unreachable” when receiveing messages from the server

(Note: I moved this question from StackOverflow, because it's to be considered off-topic there, better fits here, and still unsolved) I have a udp client using luasocket, basically doing this (with a ...
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1answer
173 views

Public wifi on public bus blocks all udp packets [closed]

Our public bus service gives us free WiFi but all UDP packets are blocked because I couldn't play online games that uses the udp protocol or make voip calls on my android phone. I ran a test on the ...
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2answers
191 views

Is there a simple audio player that can be remote controlled with UDP or TCP commands? [closed]

Is there a simple audio player that can be remote controlled with UDP or TCP commands? The control needed is very simple: Stop Play Pause Volume up Volume down Next Track Previous Track
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82 views

Is it possible to edit TCP and UDP packets?

Is it possible to edit the UDP and TCP packets a program sends? For example, we have a program that sends some information to its server. But we don't want to send some information that might be ...
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300 views

UDP port binding to loopback interface

I've been trying to play a video game in multiplayer, but after trying a lot of time, I begun to realize there was some problem with my loopback interface (Windows 7) I have UPnP activated in my ...
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1answer
603 views

How to sync two looping videos with mplayer and upd?

I am trying to sync two instances of mplayer with -upd-master and -udp-slave, and notice that the slave staggers for about a second when the master begins the loop anew. I am running debian 7.1 with ...
2
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1answer
535 views

TCP vs UDP. Sending data on a closed port

I try to understand differences between TCP and UDP packet on the error-checking. I know that UDP packets are connectionless and doesn't care that the packet will arrive the destination safely. And ...
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2answers
13k views

For what does ssh use UDP?

Wile doing research I noticed that SSH both uses TCP and UDP. I completely understand the use of TCP, but UDP seems a bit strange. Why would I use an "unreliable" transport protocol with minimal ...
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3answers
77 views

Changing the ports a program uses

This question might not even make sense. I have a very limited understanding of how networking protocols work. My phrasing of these questions might be very poor. My school has a firewall enabled. ...
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2answers
560 views

UDP Flood to Host in the firewall logs

When the router's firewall logs shows as follows UDP Flood to Host PRIVATE_LAN_CLIENT_IP, PORT ->> EXTERNAL_PUBLIC_IP, PORT (from WAN Outbound). Will those packets be routed to the private lan ...
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302 views

How to use netperf on specific NIC port?

I have two servers, SERVER and CLIENT and each server has its own onboard 1 GbE ports, and its own NIC with a 10 GbE port. SERVER and CLIENT are interconnected on both a 1 GbE switch (administrative ...
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3answers
1k views

How to force a process transmit over UDP instead of TCP?

I 'm running an ffserver process on a Linux machine, in order to achieve video streaming via ffmpeg. However, there is a delay on video streaming. On ffserver configuration file I define Port 8090. ...