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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UDP Port Forwarding and outgoing port

For UDP, assume that an incoming port (say X) is forwarded onto a port on a local host (say Y). Does that guarantee that any outgoing traffic from port Y from the local host appears as traffic from ...
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What is the master process running on port 465?

I want to close non used ports in my server, after doing a port scan I found service urd running on port 465. Running lsof I see a "master" process running on that port (also 25, 587,etc..). Question ...
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How to generate UDP packet

I want to generate UDP packet to test a program, something equivalent to using telnet to test TCP port (Can telnet generate UDP packet?) How can I do this?
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3k views

UDP blocked by Windows XP Firewall when sending to local machine

I work for a software development company but the issue doesn't seem to be programming-related. Here is my setup: Windows XP Professional with Service Pack 3, all updated Program that sends UDP ...
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1answer
48 views

TCP throughput much better than UDP

I'm monitoring the performances of a WAN link with iperf between two windows machines on both ends. Surprisingly (for me), TCP single session default window reaches a throughput of 12Mbps, while UDP ...
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1answer
2k views

OpenVPN working with TCP not with UDP

I have successfully set up an OpenVPN server on Debian (raspberry pi model b+). With the protocol set to TCP it works exactly as desired (internet routed through VPN, access to local network machines),...
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14k 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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Netcat/socat behavior with piping and UDP?

I guess this is close to linux - Netcat stops listening for UDP traffic - Super User, but I thought I'd better ask anyways As far as versions of netcat I'm using Ubuntu 11.04 and the default netcat ...
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56 views

UDP Short packet

My mychine is probably under some kind of DoS attack, my syslog is full of: kernel: [5618300.661196] UDP: short packet: From 119.37.12.102:53 4103/1480 to x.9.158.119:3604 kernel: [5618300.663014] ...
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What does SSH use UDP for?

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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30 views

can you allow only Ethernet packets destined to a certain MAC address through a network adapter?

I would like to transmit UDP ethernet packets from my PC to custom hardware (of known MAC address) which is directly connected with an ethernet cable using no switches. Different services on the PC ...
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31 views

Does Transmission Bittorrent client use UDP?

I am running a Transmission Bittorent server to upload various Linux ISOs. I am currently being flooded by UDP packets. I mean the DoS protection in the Archer C5 home router and it blocks parts of ...
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855 views

VPN for specific UDP ports?

My ping to DotA 2 servers (online video game) is very poor in afternoon hours. My ping usually go as high as 300ms or even more. I tried to use OpenVPN with my dedicated server my ping decreased to ...
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Proxifier that supports UDP? [closed]

Im looking for a proxifier that forces all Windows traffic through a specific proxy. I have my own server so I can ultimately configure any type of proxy (Socks, HTTPS, etc) so thats not a problem, ...
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1answer
5 views

How would I do a GET and parameters requests in ncat using udp?

I'm trying to learn the difference between http and udp. So how would I request via udp: udp://server/path_name?param1=value1&param2=value2 Theoretically is that kind of thing possible or am I ...
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1answer
23 views

DrayTek Vigor 2830 open port issue

We're using a Vigor2830 for routing VoIP/SIP traffic. One of the ports required to be open is 5090 for TCP/UDP. Going into the open ports section of the Vigor menu we have opened all the ports ...
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15 views

UDP fails horribly after waking from sleep (and maybe without sleep too)

We've got a PC running Windows 7 Home Premium that fails in a rather odd way after waking from sleep (and possibly other times as well, we haven't been keeping detailed records). The most obvious ...
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How to use UDP hole punching for a SSH tunnel / session

I want to deploy a Raspberry Pi in my weekend cottage. The Raspberry Pi is there to log the temperatures and send them to a remote server which has a fixed ip, saves the data and displays it on a ...
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56 views

Why is there no UDP port forwarding in SSH?

I know SSH can forward TCP ports, not UDP. I'm not seeking help to circumvent this restriction (this subject is covered here). I'd like to know what is the reason SSH never got UDP forwarding ability....
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349 views

Tunnelling TCP connection through NAT

My server is in my school's NAT and my desktop computer is in my home NAT. I want to SSH to my server from home. I normally used school's VPN, but recently for some reason I can't. So I'm looking for ...
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1answer
1k 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 ...
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2answers
4k 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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40 views

Control excessive outbound traffic

Ubuntu server is sending outbound request excessively. I am not sure why this happening. Following is the output I am getting for tcpdump root@demotrt:~# tcpdump -n -n port 53 tcpdump: verbose ...
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Sending ihex file over UDP using sockets

I am working with IPv6 and UDP sockets using python-2.7. I am particularly focusing on IPv6 Multicasting ff02::1 where every Link-Local address device (with fe80::) responds to queries from a central ...
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44 views

Can two different applications bind the same port on a host if they use different protocols?

my question is quite clear I think. If two applications use different transport layer protocols (e.g. TCP and UDP or something else) can they open the same port number? How does the OS do the ...
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UDP Forwarding redirection keeping source info in Linux

I would like to do an UDP Forwarding redirection of traffic in machine B, so UDP traffic from machine A would go to machine C. I have used iptables and that goes fine. The problem I have is that I'm ...
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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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How to ask router for bandwidth statistics?

I once heard that there is a UDP protocol for asking a router how much data has moved through it per minute, but a simple Google search did not help me identify it. What is the protocol called, and ...
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31 views

TCP and UDP do not work with firewall

I can not connect my TCP-Client to my TCP-Server. Here is my Code: http://stackoverflow.com/questions/35661591/tcp-server-does-not-work-with-firewall I have already opened my TCP-Port "8888" in the ...
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2answers
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Why ICMP is different that TCP and UDP? [closed]

what is the difference between Internet Control Messaging Protocol over Transmission Control Protocol and User Datagram Protocol
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301 views

Understanding “cat proc/net/udp”

# cat /proc/net/udp | egrep "sl|3ADBFE0A" sl local_address rem_address st tx_queue rx_queue tr tm->when retrnsmt uid timeout inode ref pointer drops 16: 3ADBFE0A:007B ...
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Does it matter what UDP port a WOL signal is sent to?

i have seen many WOL instances use port 7 and many use port 9, does it matter? Isn't it just looking for a WOL packet at layer 2 or ethernet?
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Is ICMP port unreachable error generated by both TCP and UDP? [closed]

A program on machine X attempts to open a UDP connection to port 5376 on a machine Y, and a TCP connection to port 8632 on machine Z. However, there are no applications listening at the corresponding ...
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What is a simple STUN test I can perform from a Windows machine?

I want to test whether someone else's Windows machine can access a public STUN service using UDP and receive a response on its network, which I expect is behind a NAT and firewall. I do not have ...
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UDP port 9987 wont open on my firewall

I have a zywall-usg-200 and i have tried to open ports, i managed to open two TCP ports but the UDP port 9987 fails, cant connect to it. Does anyone have the same problem? Or is it just my firewall
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DNS Resolver for Windows over TCP

I know that DNS uses UDP with Port 53 for DNS queries. However, at my place sometimes UDP requests are blocked and DNS fails. I know that there is protocol for DNS over TCP and many public DNS servers ...
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UDP “connections” rejection

I'm managing (edit: is hosted by VPS hoster) small machine for couple of game servers and website server (apache) together with some friends. Problem is firewall sometimes drops UDP packets. The ...
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Read UDP packages created by another computer

Laptop 1 Laptop2 192.168.1.103 192.168.1.120 Ubuntu Windows 8 ? <-- Matlab: UDP I use MATLAB software on my windows and I ask it to generate real ...
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NTP not getting through even to DMZ

My home router seems to be blocking UDP 123. sudo ntpdate -u time.apple.com works as expected, but sudo ntpdate time.apple.com I get: "no server suitable for synchronization found" I can get a ...
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Why do UDP Packets stop being sent if TTL Expire message received?

I have a program that sends UDP packets to devices as part of a task. If during this task, any of the targeted IP addresses causes a TTL Expired packet to be received, the program can no longer get ...
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WiFi UDP unicast vs. multicast speed

From what I have gathered UDP multicast / broadcast over WiFi will not yield the speed as one would have thought. What about UDP unicast over WiFi? Can anyone confirm that the latter will have a ...
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What is the reason for speed jumps in this Wifi transmission?

In this picture: The X axis is time slots of 5 seconds each and the Y axis is the number of 1KiB packets transmitted in that slot. The blue graph shows the actual number of transmitted packets ...
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37 views

Capture only UDP traffic that cannot be identified as another protocol

I have applied the udp filter in order to just capture UDP traffic, as described in Wireshark Wiki: Show only the UDP based traffic: udp However, this does not only show UDP traffic. It shows ...
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186 views

How to stream video by using UDP VLC player?

I am trying to stream the video and this is what I did. start C:\Progra~2\VideoLAN\VLC\vlc udp://@:60000 start C:\Progra~2\VideoLAN\VLC\vlc.exe C:\Progra~2\VideoLAN\VLC\FullDuplexRadio.3gp --sout=#...
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Looping back network traffic on the same machine

I have some 3rd party software that expects UDP traffic to/from other machines on the same UDP port. I want two instances to run on the same machine and talk to each other. I'm running it in Windows7....
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35 views

unknown local address in TCPView

I'm looking at connections in TCPView, and I'm seeing "red5" in the "local address" column. This doesn't appear to match any computers on my local network, the names of which I have seen from time to ...
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Multiple UDP servers at same port, only locally?

Someone sends a UDP packet over the internet to a router public IP and port. Can this packet reach all the PCs of the LAN (using broadcast?) if they are listening on the port for UDP ?
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simulation gets disconnected from adhoc network when working with UPD blocks

I'm working with MATLAB simulink and trying to send data using UDP block from a model running on external mode (on a quad-copter which runs on linux ) to a model running in normal mode on my computer ...
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80 views

Broadcasting with socat via UDP, timeouts (maybe package lost?)

I want to setup a small broadcaster. I capture the stream from a program via UDP and broadcast it through the network (from IP *2 to *32, because just maximum 32 devices are connected). If I give ...
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2answers
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Linux built-in or open source program to join multicast group?

I'm using tcpdump to capture multicast packets and had to code up a custom program to join multicast feeds so tcpdump will "see" the packets. Just wondering if netcat or any other applications can ...