Skip to main content

Questions tagged [udp]

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.

Filter by
Sorted by
Tagged with
0 votes
0 answers
26 views

In Linux, if creating a TCP map with a port forwarder to a SOCKS5 proxy server, being them listening in different IPs, UDP associate doesn't work

In Linux, when I forward a TCP port with a port forwarder (such as socat) to a port of a local SOCKS5 proxy server, I can connect to the first using UDP (UDP) only if the port mapped with a port ...
przemyslawo's user avatar
0 votes
0 answers
44 views

How to improve performance of unicast to broadcast UDP packet transformation on OpenWrt?

Background We have some devices sending unicast UDP packets which we want to receive on multiple computers by transforming those packets to broadcast. We can't make any changes to the devices sending ...
Linus's user avatar
  • 288
0 votes
1 answer
84 views

iptables duplicate port traffic

I want to clone/duplicate all udp traffic incoming on port 8500 to port 8600. It is important that the source address is not modified. Also both ports must be accessible by applications (the packets ...
mirokai's user avatar
  • 43
0 votes
0 answers
14 views

Application does not get mulicast messages on ubuntu os

I have an applicaion running on ubuntu 16.04 os. The application is receive mulicast messages however the application does not get the messages. I can see on wireshark IGMP message that the ...
Ala's user avatar
  • 1
0 votes
0 answers
36 views

What's the best way to support mosh behind NAT to multiple hosts?

Mosh requires that you port forward UDP ports 60000 to 61000 to your host (unless you specify different ports.) If you have three hosts behind NAT, for instance, that you want usable with mosh, how ...
user606723's user avatar
10 votes
2 answers
1k views

How to receive UDP packet with 127.0.0.0/8 dst address in userspace

I would like to know if it is possible in linux to receive an UDP packet in userspace that has a 127.0.0.0/8 dst address but coming from an external interface. I tested it with nc and I can see ...
zskr's user avatar
  • 103
0 votes
1 answer
44 views

Does my office/lab server need to be providing these services?

I'm trying to figure out what services my university Ubuntu 22.04 computer needs to provide to other machines. I often ssh into this machine and other computers in my lab use it as an NFS server. I ...
mikemtnbikes's user avatar
0 votes
1 answer
59 views

Heavy UDP/sunrpc network usage to unknown IP addresses

In the last week or so, my network monitory has indicated that my desktop computer has started periodically sending ~0.7MB/s out over my ethernet connection (eno). I understand very little about ...
mikemtnbikes's user avatar
-3 votes
1 answer
99 views

What is the counterpart of telnet client for servers based on UDP?

Telnet client is said to communicate only with servers which are based on TCP, not with those on UDP. What is the counterpart of telnet client for servers based on UDP?
Tim's user avatar
  • 103k
0 votes
4 answers
533 views

Is it "telnet:" or the port 4161 that is telling me that I'm connecting to an UDP server?

I am asking this question because I am not meeting UDP and telnet often... To prepare myself for a development, I am reading a documentation where I will have to connect to a telnet://x.y.z:4161 url. ...
Marc Le Bihan's user avatar
1 vote
1 answer
125 views

Can nc send message from client to server on a udp port?

Both client and server are Debian 11 On Server as root: nc -ulp 1194 On Client as root: nc -u serverip 1194 When I type something on client, in theory it should appear on the server right if no ...
rocky_alpine's user avatar
0 votes
1 answer
95 views

I can't block a port with ufw

This morning I received a report from Netscan: Netscan detected from host 8X.19X.1X.1XX time protocol src_ip src_port dest_ip dest_port Fri Sep 15 05:21:59 2023 UDP 8X.19X.1X.1XX 5065 => 9.87.179....
Willy Makend's user avatar
0 votes
1 answer
500 views

Is NFS proto=udp supported in RHEL 8 nfs-utils-2.3?

I can get vers=3 to happen, and I can get mountproto=udp to happen, but I cannot get a proto=udp to happen on the nfs client. I can only get proto=tcp on the nfs client. Is proto=udp supported in nfs-...
ron's user avatar
  • 7,239
2 votes
2 answers
2k views

difference NFS proto and mountproto

in RHEL 8.8 when I am trying to test NFS tcp versus udp and versions 3 versus 4.0, 4.1 and 4.2, I observe on my nfs client a mountproto= in addition to proto= when typing mount. What is the ...
ron's user avatar
  • 7,239
0 votes
1 answer
428 views

How to send UDP broadcast datagrams to port below 1025?

Scenario I'm trying to send a UDP datagram message with socat to a broadcast address. On the receiving end this is how I'm running socat (with root privileges): socat UDP-LISTEN:1011 - I'm trying to ...
polemon's user avatar
  • 11.6k
-1 votes
1 answer
458 views

openvpn client cannot connect via UDP, but TCP works fine

problem: I've setup a new ubuntu 20 vm on esxi and installed openvpn. It can connect to multiple vpn servers, like protonvpn, but only through tcp, not udp. troubleshooting: Used netcat to verify ...
rigged's user avatar
  • 1
0 votes
1 answer
108 views

Traceroute from VM guest does not go past Host PC to internet

I have created an Ubuntu virtual machine on my PC, and I was trying out the traceroute command, as I need it for a college project. However, when I ran "traceroute www.google.com", what I ...
Boni Daniel's user avatar
0 votes
0 answers
690 views

understand different UDP packet loss results: iperf3 vs nuttcp

I try to measure UDP [%packet loss] between two machines. I'm getting different results while using two different tools: iperf3: machine 1: iperf3 -s machine 2: iperf3 -c <machine_1_ip> -u -...
hutcruchi's user avatar
  • 349
2 votes
1 answer
1k views

Can i trust echo result of nc command for UDP?

Context : I want to test UDP port with nc command What happens : nc command return nothing on output and 0 when i put echo $? Which command : nc -vzu <ip> <port> echo $? What is the ...
adhara's user avatar
  • 23
0 votes
1 answer
422 views

Ncat very slow over UDP. Possible causes?

I've got three servers, "a", "b" and "c", all in same /24 subnet mask. On all of the servers, to any of the two other servers, nc to TCP port 9999 consistently takes 0.01 ...
RonJohn's user avatar
  • 1,144
0 votes
2 answers
2k views

Check whether SOCKS5 proxy server support UDP

Suppose I have UDP server that listen incoming message on 192.168.43.1:1234 and SOCKS5 proxy server that listen on 192.168.43.2:9999. How do I check whether SOCKS5 proxy server support UDP when ...
Muhammad Ikhwan Perwira's user avatar
0 votes
1 answer
131 views

command that shows all online connections?

I used TCPView to see all TCP and UDP endpoints in Windows. Is there any linux command/gui that has similar functionality?
ant4598's user avatar
1 vote
0 answers
46 views

facing isue in UDP multicasting after changing ip of the device

we have a requirement for UDP multicasting in our project using Linux 4.1 kernel with static ip address. basic UDP multicasting using sendto function to send data is working fine with device static ip ...
Rajesh's user avatar
  • 11
1 vote
1 answer
181 views

socat tunnel traffic drops after some time

I have two Linux machines, I want to create a tunnel between them using socat, this is my workaround: Machine1: socat -d -d UDP-LISTEN:4711,reuseaddr TUN:10.50.50.1/24,iff-up,iff-broadcast,iff-...
abexamir's user avatar
0 votes
0 answers
244 views

Is there a good way to balance UDP packets over multiple ports?

I'm not really sure where to turn, so I'm hoping that someone can help me out. My ISP is very aggressive with various types of throttling. It throttles UDP traffic by port. With incoming UDP traffic ...
Mir's user avatar
  • 1
0 votes
0 answers
189 views

Is it possible to make the softirq run on the core the user wants?

My system: NIC: ConnectX5 MCX516A-CCAT (100GbE NIC) OS: Ubuntu 22.04 LTS CPU: Intel Xeon Silver 4314 (Dual CPU, 16Core + 16Core) I'm doing UDP communication using a 100GbE NIC. However, if the task ...
james1313's user avatar
0 votes
0 answers
37 views

Why do udp requests fail temporarily

I've a UDP web server, which bound to the port 10000. I just deployed it on the server 172.20.0.10. Then I tried to scan the port nc -v -z -w2 -u 172.20.0.10 10000, it seems that everyting is OK. The ...
Yves's user avatar
  • 3,331
0 votes
0 answers
32 views

Is it possible to detect if a process is trying to create a socket connection but the remote server refused

Let's say that I have a process on my local Ubuntu. I want to know if it would use some socket connection(TCP or UDP) to connect some remote server, which has been turned off, meaning that any ...
Yves's user avatar
  • 3,331
0 votes
2 answers
1k views

Check what service is running on a specific tcp/udp port

I'm looking for a command-line utility that allows me to check what service (eg: http/ftp/ssh) is running on a specific port of a remote machine. An example of how I imagine a program like this would ...
kess's user avatar
  • 123
0 votes
0 answers
483 views

socat streaming UDP is slower than TCP

I'm currently using subprocess.run(["socat", f"udp-listen:{_to},fork,reuseaddr,bind=127.0.0.1", f"""exec:'sudo ip netns exec {netns} socat STDIO "UDP-connect:...
DrownedSuccess's user avatar
0 votes
1 answer
388 views

socat does not honor sourceport option

I am trying to send a udp packet from a specific port: $ echo hello | socat - UDP-DATAGRAM:192.168.1.255:11111,broadcast,sourceport=22222 But a random port is used instead: # tcpdump -vvvv -ttttt -...
Evgeniy Berezovsky's user avatar
1 vote
0 answers
714 views

Using UDP multicast in Linux, recvfrom() cannot get data

I have a task to get data from a sensor device. Through the Wireshark, I can capture information as below: wich send information from 10.13.1.113 to 224.0.2.2 (Multicast Address). Src Port 42402, Dst ...
LincolnYang's user avatar
0 votes
1 answer
349 views

Does the correctness of MAC address matter in UDP?

Here is the thing, I used tcpdump and created a UDP-only pcap file from production environment. Then with the tool tcprewrite, I updated the UDP packets dst IP and MAC address as vm2, src IP as vm1 ...
chengdol's user avatar
  • 183
0 votes
1 answer
717 views

Blocking UDP port 140 from receiving packets from source port 8989 (active way to send signal to sender that is unreachable)

So my problem is that I want to block UPD port 140 from receiving packets from port 8989, but I want to block it actively, not just silently ignore it, but to send an active signal to the sender of ...
Diar Kryeziu's user avatar
1 vote
1 answer
381 views

TCPDUMP IP UNKNOWN

I am seeing this in the tcpdump output 21:32:51.580969 IP UNKNOWN.9998 > 255.255.255.255.9998: UDP, length 12 What does 'IP UNKNOWN' mean? Is something hiding the ip address? Thanks
user667522's user avatar
1 vote
1 answer
343 views

Is there a tool to count the latency of UDP datagrams in Linux?

Now I want to test the network performance between two Linux systems. The test scenario is as follows: one terminal sends UDP datagrams to the other terminal continuously at fixed intervals (the ...
fooh's user avatar
  • 11
3 votes
0 answers
1k views

what does `IgnoredMulti` statistic for Udp in debian linux mean?

I have a Ubuntu machine that is receiving UDP packets by joining a multicast group, occasionally we are getting UDP packet drops. when I am trying to monitor using netstat -s I get the following ...
Anirban Bhowmik's user avatar
0 votes
1 answer
2k views

How can I send a UDP packet from my Linux ASUS router?

I have changed the firmware on my router, unanme -a yields: Linux RT-AC86U-8458 4.1.27 #2 SMP PREEMPT Fri Aug 6 18:32:35 EDT 2021 aarch64 ASUSWRT-Merlin I have logged in to ssh to this router, and I ...
birgersp's user avatar
  • 311
0 votes
1 answer
266 views

NFS client won't list files when using UDP

I have an NFS server (server1) that works fine with TCP, but when a client mounts it with UDP, while the mount point works, it can only list folder with no files in it. If there's a file in that ...
joovunir's user avatar
-2 votes
1 answer
293 views

How to get open connections statistics without ss or netstat

The question may sound silly but I'm trying to make a tool that uses ss data. Sadly I'm having some troubles regarding output format parsing (too much randomness depending on version and system). So, ...
PabPabPab's user avatar
0 votes
1 answer
448 views

How to drop all unnecessary UDP traffic on INPUT chain?

About 2 weeks ago, I started running a Tor relay, which itself operates solely on TCP. So, I would like to drop all UDP packets, which are unneeded. But I don't know, what is actually needed (if ...
Vlastimil Burián's user avatar
0 votes
0 answers
427 views

tcpdump, determine transport protocol

Is there a easy way to determine the transport protocol of a packet by looking at the output of a TCP dump trace? I'd just like to be able to tell if a packet is UDP or TCP. I've tried using the -x ...
Frank's user avatar
  • 129
0 votes
0 answers
759 views

Low-level tcp/udp proxy

Is it possible to set up a server which acts as a proxy that is able to delegate all incoming traffic (regardless of protocol) to the original destination? What I am trying to do is to allow only a ...
orange's user avatar
  • 187
0 votes
1 answer
759 views

Iptables Accept All From Specific Ip And Port

I want to accept all traffic that is coming from an IP address and its specific port to any of my ports. Here is the configuration: Details: I am using Jitsi in a server, and I want to reach Jitsi ...
sahin's user avatar
  • 1
2 votes
1 answer
1k views

How to setup veth with 9000 MTU to simulate sending and receiving large UDP multicast packets on the same host?

The sender needs to transmit large data packets to the receiver (which is on the same host with 1500 MTU) and I think this can be simulated using veth with 9000 MTU, from my reading on it. But I'm not ...
Anand's user avatar
  • 23
0 votes
0 answers
338 views

Only Flatpak apps can open all websites after connecting to VPN

I'm using PureVPN app (openvpn/udp). Installed via rpm file. After connecting, If I ping youtbue.com it shows: --- youtube.com ping statistics --- 7 packets transmitted, 0 received, 100% packet loss, ...
ICE's user avatar
  • 101
0 votes
1 answer
1k views

reordered and duplicated packets when using UDP over loopback interface

We are seeing UDP packets being reordered and duplicated when being sent over lo. We can see this because we're sending MPEG transport streams, which have their own sequence number in their headers, ...
Nathan Commons's user avatar
0 votes
1 answer
285 views

linux bridge interrupts udp packet flow

I am having a UDP issue with the following bridging setup (Linux 5.11.6): (let ns${i} denote namespaces and left${i}/right${i} be veth pairs) ns1{right1(x.x.x.1)---}---ns2{---left1::bridge(x.x.x.2)::...
rednexela1941's user avatar
0 votes
1 answer
469 views

Script that performs an action based on the contents of a UDP packet?

I'm trying to write a script that listens for broadcasted UDP packets on port 2088, read the data, and then POST to an URL. Specifically, I'm trying to make a LIFX light turn red when I'm on the ...
pooter03's user avatar
  • 113
0 votes
1 answer
2k views

Netcat listener: Line break between syslog messages

I am playing with netcat command. On this linux system, I have set up a netcat listener on UDP 514, so that I get to see syslog messages from remote systems. $ sudo nc -v -ulp 514 listening on [::]:...
Bruce Malaudzi's user avatar

1
2 3 4 5