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1
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2answers
47 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, ...
1
vote
1answer
25 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 ...
2
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0answers
34 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 ...
1
vote
1answer
59 views

tcpdump and nc with udp

I don't understand the behaviour of netcat. Let's say that I have one host acting as server: [root@localhost tmp]# nc -u -l -p 670 Then I try to connect from a client: root@debian:/tmp# nc -u ...
2
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0answers
155 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
votes
1answer
236 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 ...
0
votes
2answers
80 views

UDP sending two strings in a datagram

I'm wondering if its possible to send two strings within one datagram in a UDP packet. Assume I had string 1 with text: unix and string 2 with text: linux. I don't want to merge the strings but keep ...
12
votes
1answer
3k 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 ...
2
votes
2answers
1k 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 ...
2
votes
1answer
776 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 ...
3
votes
1answer
1k 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 ...
2
votes
0answers
2k 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 ...
0
votes
1answer
62 views

How to log all udp packets from port N in readable format?

How to log into file all udp packets (in and out) from port N in readable format (capture packet type (time stamp, name of error if one happens or message type, data size, data))?
0
votes
1answer
302 views

UDP commands for Linux and Mac?

I'm trying to test UDP between 2 terminals in the same machine. For instance: Terminal 1 UDP listener@port:3000 UDP sender to port:3001 Terminal 2 UDP listener@port:3001 UDP sender to ...
1
vote
2answers
164 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 ...
11
votes
1answer
2k views

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 - ...
2
votes
2answers
2k views

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 ...
1
vote
0answers
85 views

setting up a local VoIP to use as a Wifi Headset

I had this idea of using Wi-fi in a vehicle to connect my cell to the car call handler.Just as it works with bluetooth nowadays. Just to demonstrate that such a thing is possible , i had three Linux ...
3
votes
1answer
246 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 ...
1
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0answers
108 views

Command for finding open ports

On my linux servers I have this alias set: alias ns="sudo lsof -Pi|grep -v ESTABL|grep -v CLOSED|grep -v -e '->' | tr -s ' ' '\t' | awk '{print $3 "\t" $8 "\t" $5 "\t" $9 "\t" $1}'| column ...
0
votes
0answers
112 views

How to make Network alive but speed low, slow for upload, download?

I have own application written (Python, Java) which does upload/download for streaming. Now in my local office network and home network setup i can't simulate slow/low latency network (as a result i ...
3
votes
1answer
2k 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 ...
3
votes
1answer
60 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 ...
0
votes
1answer
79 views

How do I verify that the Linux kernel is not freezing when uploading or downloading large data over the ethernet interface?

How to verify if the Linux kernel is doing what it's saying for network interfaces? I have one network interface eth0 which has hardware support to do 1GB full-duplex. I have prepared 2 box. Now ...
2
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0answers
183 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 ...
1
vote
2answers
91 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 ...
1
vote
1answer
922 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 ...
2
votes
0answers
325 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 ...
3
votes
1answer
115 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 ...
2
votes
1answer
657 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
votes
1answer
669 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 ...
0
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0answers
431 views

Tools to find OpenVPN UDP packet corruption

Are there Unix tools to troubleshoot UDP packet corruption? I'd like to avoid writing my own... I think ping might report when a packet is corrupted, but it doesn't really seem to have options ...
4
votes
1answer
162 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 ...
1
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0answers
94 views

Cannot see an EC2 VPN server from another EC2 instance

I'm using openVPN to connect to one EC2 instance from another. The client cannot see the server, however, despite that servers outside of AWS can see the server and successfully negotiate with it. ...
1
vote
2answers
278 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 ...
3
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0answers
934 views

I can SSH and HTTP, but not ping or access particular UDP services over my LAN

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
votes
0answers
655 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 ...
1
vote
1answer
2k 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 ...
4
votes
1answer
2k 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 ...
3
votes
1answer
707 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
3k 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, ...
2
votes
1answer
463 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
2answers
457 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 ...
3
votes
2answers
639 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 ...
0
votes
1answer
354 views

recvfrom() doesn't get any request from any remote client

I have written a udp server which receives client requests using a recvfrom() socket system call, this call receives requests from localhost only, no remote host requests are seen by the recvfrom() ...
2
votes
2answers
324 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 ...
9
votes
3answers
11k views

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 ...