User Datagram Protocol (UDP) is defined to make available a datagram mode of packet-switched computer communication in the environment of an interconnected set of computer networks. This protocol assumes that the Internet Protocol (IP) is used as the underlying protocol.

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Is it better to set -j REJECT or -j DROP in iptables?

There's an example of iptables rules on archlinux wiki: # Generated by iptables-save v1.4.18 on Sun Mar 17 14:21:12 2013 *filter :INPUT DROP [0:0] :FORWARD DROP [0:0] :OUTPUT ACCEPT [0:0] :TCP - [0:0]...
12
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12k views

Why is my TCP throughput much greater than UDP throughput?

I haven't done anything unusual to my hardware or kernel configurations (all default settings, fresh OS install, Linux kernel 3.11 TCP/IP stack) and I'm averaging about 3.83 million messages per ...
12
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3answers
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How do I reserve ports for my application?

How do I reserve a list of ports for my custom applications? To be specific, the product I'm creating has a lot of processes and a lot of intercommunication between them. The problem I'm having is ...
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3answers
6k views

How does netcat know if a UDP port is open?

So I can use this netcat command to check if a UDP port is open: $ nc -vz -u 10.1.0.100 53 Connection to 10.1.0.100 53 port [udp/domain] succeeded! Unlike TCP, UDP is connectionless (fire and ...
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How can I redirect all UDP traffic from one port to another on BSD / OS X?

On Mac OS X 10.9.5 I am running boot2docker and would like to temporarily forward a non-privileged UDP port 69 to port 69 of the boot2docker virtual machine. Virtualbox only supports forwarding ...
5
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1answer
2k views

Centos 6.3 Server ignoring IGMP Queries

I am using a CentOS 6.3 server to subscribe to UDP multicast data, and I noticed that my server doesn't answer the IGMP queries sent by the switch it is connected to. As a result, when I open my ...
4
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2answers
1k views

How to listen to all ports (UDP and TCP) or make them all appear open in Debian

I got an external Debian server. The problem is that my university campus doesn't allow connections to go outside when the port is different than TCP port 22, 80, 443, or UDP port 123. I tested them ...
4
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1answer
4k views

Run nmap via Tor

Is it possible to runnmap via Tor? When I googled around, I got the impression that Tor uses Polipo / Privoxy, which are socks5 proxies. So any TCP / UDP aware applications should be able to use them ...
4
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1answer
234 views

Alternative to DNS for internal servers

I am setting up my first network at work. All the servers are running CentOS 6.3 and have statically assigned IP addresses. For example: server1 192.168.0.101 server2 192.168.0.102 I want to be ...
4
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1answer
7k views

TCP buffers keep filling up (Recv-Q full): named unresponsive

Using netstat -an, I set the message that the Recv-Q is full. It is filling up to the rmem_max: Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address ...
4
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1answer
2k views

why ss(8) understands listening UDP ports differently than netstat(8)?

If I execute ss -lu in order to view all the listening UDP sockets, then none of the sockets are displayed. If I execute ss -au, which lists all(both listening and non-listening) UDP sockets, then "...
4
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1answer
4k views

Why would my Linux host suddently stop receiving multicast? All other nics on private network are receiving

Here is my dilemma. Suddenly, as of yesterday, multicast packets are no longer being received from eth1 (private gigabit network) from one node. Routing between all the nodes is fine, no collisions, ...
4
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1answer
147 views

What are the requierements to sniff UDP packets in a Wireless Ad-Hoc network?

In a wireless Ad-Hoc network, I have two computers which communicates in UDP together from 192.168.1.3 to 192.168.1.5 I have a third computer (192.168.1.6) which wants to listen to the packets which ...
3
votes
4answers
140 views

Mass IP Blocking

I have a game server and someone is spamming it with bots. The SpamBot client makes the handshake with my server using UDP connections. It does this through a list o proxies. Basically, the Spambot ...
3
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2answers
877 views

Bash: Permission denied when trying to echo data directly to Network

I am trying to send characters directly to the network stack as explained in this thread. Even when the process work OK under CygWin (Windows), the same lines do fail on Ubuntu v14.04: luis@...
3
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3answers
11k views

Multicast UDP not working

Multicast UDP on raspberry pi I haven't narrowed things down enough to know if my issue is because of debian, raspbian specifically, or if I am just missing a something completely. I have a python ...
3
votes
1answer
7k views

How to use netperf on specific NIC port?

I have two servers, SERVER and CLIENT. 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 ...
3
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1answer
550 views

listen to a conversation using port forwarding

I have been able to make a phone calls using the SIP client Pjsua from one Linux computer to another one. In case you have not heard of this user agent, explaining it's functionality is quite easy. It ...
3
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1answer
1k views

Why isn't my application receiving broadcast packets?

I have written a Qt application that listens for UDP broadcast packets on the network interface p2p1. I have installed the application in Fedora 17 i386 in a VirtualBox VM. For some reason, the ...
3
votes
1answer
78 views

Per executable UDP port redirection possible?

I have a black box program which listens on a particular UDP port. I'd like it to listen to a UDP port of my choosing. Is there a way to trick the executable into listening on a differen port. I ...
3
votes
0answers
6k views

Dumping multicast UDP stream with socat

I am setting up video streaming. In local network, there are two devices streaming video over UDP multicast. One is regular computer with Linux (streaming to 239.220.221.10, port 9200), second one is ...
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I can SSH and HTTP, but not ping or access particular UDP services over my LAN [closed]

So I've encountered a weird problem when trying to set up a Linux server running a variant of CRUX Linux. I am trying to configure it to be a Teamspeak server, but no clients can connect. The ...
2
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1answer
813 views

enable echo service and linux security loophole issues

in order to enable the echo service we need to add the echo lines as the following example : more /etc/inetd.conf echo stream tcp nowait root internal echo dgram udp wait root ...
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2answers
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What does 0.0.0.0:* mean in netstat?

Could anyone explain the following output of netstat -plunt? udp 0 0 0.0.0.0:58262 **0.0.0.0:*** 1163/avahi-daemon: udp 0 0 0.0.0.0:17500 **0.0.0.0:***...
2
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1answer
288 views

socat/netcat UDP to TCP

I am trying to bridge a connection between UDP and TCP. The UDP - must listen on port. The TCP - must connect to a server. The purpose of the connection is to control VLC player. I tried netcat and ...
2
votes
1answer
3k views

tftp transfer painfully slow

I am using HPA's tftp server for PXE boot. When I try downloading an image from my tftp server using curl, the transfer rate is less than 3 MB/s, even on my 1Gb network. curl -o initrd.gz tftp://192....
2
votes
1answer
4k views

Scan one or all ports, on UDP or all protocols, to see if I'm getting, what I suppose to get

I have a GPS localizer (TK102). I've set it up to send responses over GPRS to particular IP and over particular port. I was told that, it uses UDP. It seems that something is being sent (paid ...
2
votes
1answer
356 views

A program like nethogs for udp?

I use a good program: nethogs,is like a "top" for tcp traffic someone know something similar for udp? I want to see the udp bandwitch used by program
2
votes
1answer
204 views

Close the neccessary Ports [duplicate]

I am using Linux Mint and I am newbie. Someone is trying to access my computer via my MAC Address and open port. I have some questions: I know that there are different type of port like TCP and UDP. ...
2
votes
1answer
650 views

nfs mount works for tcp but not over udp

I'm connecting my raspberry pi (raspbmc) with my synology nas. I have 2 mounts 192.168.0.5:/volume1/video /mnt/video nfs udp,intr,noatime,rsize=32768,wsize=32768,nolock,nfsvers=3,async ...
2
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1answer
710 views

Linux “ip route” changes source address of TCP but not UDP

When sending packets from an application that binds to a local address TCP uses a different source address than UDP. For example, bind to 10.10.0.51 (alias IP), the src addr for UDP is 10.10.0.51 but ...
2
votes
2answers
376 views

UDP multicasting broken after kernel update

I've got an embedded system which is running a stripped down Gentoo userland with a manually build kernel. The system acquires data from a PCI card and sends it out to an UDP multicast group. All ...
2
votes
0answers
42 views

Netid in ss output is confusing

I'm on an Ubuntu 14.04 x64 machine. I have something running on port 51236 and I want to know whether it's TCP or UDP. So I ran ss -an | grep 51236 and got the following output. tcp ESTAB ...
2
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0answers
276 views

Filter UDP packet in tc filter

Hello I'm trying to limiting the bandwidth on my iperf udp test (iperf -u). I use tc qdisc and class to make some assured rate and ceiling rate for it. However, I don't know what filter I should use ...
2
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0answers
210 views

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

Note: I also posted this question on SuperUser, because I'm not sure where it belongs I'm trying to establish a "console-like" connection with a National Instruments cRIO-FRC. It broadcasts its ...
2
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0answers
429 views

iptables rule to transfer UDP through a SSH tunnel

The problem I have two programs that runs on two distant computers and communicate through a specific protocol. All I know is that this protocol only communicates through UDP and uses the ports 1101 ...
2
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0answers
414 views

IPTables dropping UDP packet stream

I have a configuration where UDP packets containing encapsulated DNS data are sent to a KVM instance for processing. The KVM instance sits behind an IPtables firewall which is also doing NAT. The ...
2
votes
0answers
780 views

TPROXY for redirecting UDP on arbitrary ports

I want to intercept all UDP traffic leaving tap1. And possibly reply to e.g. DNS-requests. To accomplish this I wrote some python code listening to localhost and use iptables with a rule-set like this:...
2
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0answers
1k views

Linux bridge blocks UDP packet from tap interfaces

Introduction: I'm working on a 6lowPAN projects of Wireless Sensor Networks. Basically, I have a set of nodes (Contiki OS) which are running on a linux host. Each nodes have its own tap interface ...
2
votes
1answer
684 views

ICMP destination unreachable

I am working on an Arch Linux machine with an ethernet interface eth1. I have created the interface eth1:0 using ifconfig and given it a dummy hardware address (00:01:02:03:04:05). When I send a UDP ...
1
vote
3answers
194 views

how to get statistics of received packets on a specific udp port

my linux pc has a udp port listening, however, the application does not seem to receive any packets from this port. Is there any tool that I can use to show the number of packets received on this port?...
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2answers
120 views

Can an arbitrary process read data coming to/from a network port? How?

For example, postgres does the following as shown with lsof -i: COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME postgres 29200 postgres 8u IPv6 470362 0t0 UDP localhost....
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2answers
405 views

tcpdump captures network-wide UDP traffic, but not TCP

When observing traffic with sudo tcpdump udp, it behaves like it should: I can see all traffic which is happening in the network, even when the machine which I am using is not involved. However, when ...
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2answers
3k views

Redirect stdin and stdout to ports

I'd like to take a program P that reads from stdin & writes to stdout, but connect it to nc or whatever such that it reads from a certain port and outputs to another port. # The reading is easy, ...
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1answer
128 views

Start a service on a network request (socket activation)

I have a program that under normal activation listens on some port. I don't want the program running continuously. Is there a "quick and dirty" way to wrap the application in a shell script or ...
1
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1answer
460 views

Open UDP Ports; Can I Close Them?

I'm trying to secure my internet browsing. I just reinstalled Xubuntu 14.04 and GUFW firewall. I have 8 UDP ports open. I don't understand why. The software I currently have open are Firefox, GUFW, ...
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2answers
495 views

What ports are essential and should generally be allowed on a Linux system?

I'm running a desktop computer, but one with high threat risk. I've blocked all ports using a firewall except: HTTP, HTTPS, DNS, one port for torrent client. Do any common processes in distros ...
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vote
1answer
2k views

Command line streaming string manipulation from netcat

I have a netcat udp connection listening with nc -l -u .... I've been trying to do a per packet manipulation of the incoming data with just command line, but it doesn't look like there is a flag in ...
1
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2answers
620 views

How to find transmission speed?

Two host machine's one as a client and other as a server, i am testing udp load-test in these two machines.Machine Ethernet speed is 100 Mbps but i want to send 30000 packets each of 512 bytes at 1 ...
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2answers
509 views

UDP NAT Punching

I have the following two problems. Please help me to solve them: In symmetric NAT, as I know, the local hidden node (behind the NAT) must initiate connection in order to create a window in the NAT ...