is a data communications endpoint for exchanging data between processes executing within the same host operating system.

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How authentication is done between two nodes in tcp/ip or udp client server socket

I have a client socket program and server socket program in C TCP/IP . I execute the server program first on a port say 5000 and then executes client program on the same port and then server respond ...
2
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2answers
7k views

Installing vsftpd - 500 OOPS: could not bind listening IPv4 socket?

I have to set up a FTP server on my machine. I have installed vsftpd using the command: sudo apt-get install vsftpd I then edited the configuration file vsftpd.conf in the location /etc. The file ...
4
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2answers
64 views

What's the difference between “>&1” and “>/proc/self/fd/1” redirection?

I'm working on some script that being run by rc.local at startup, and I noticed that output redirection works quite strange. If I write something like echo "foo" >&1, it ends up in syslog, and ...
3
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1answer
54 views

Placing OpenSSH control socket in /run

OpenSSH has a feature that allows you to multiplex connections over a controlsocket. It is generally accepted that these control sockets should not reside in a common area, due to the security issues ...
3
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1answer
27 views

unbind port of crashed program

is there any way to unbind a port that was previously binded by a program that crashed at some time? I don't like to reboot the development-machine every hour.
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12 views

How to recover a screen session?

I'm running a screen session and it seems it hung up somehow. 0 ✓ user@hoster ~ $ screen -ls There are screens on: 30418.pts-2.hoster (Detached) 1 Socket in /run/screens/S-user. However, when I ...
35
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4answers
50k views

How can I communicate with a Unix domain socket via the shell on Debian Squeeze?

I’m running a Debian Squeeze web server. I’ve installed memcached on it, and configured memcached to listen on a Unix domain socket (at /tmp/memcached.sock), as it only needs to receive messages from ...
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0answers
22 views

strace for troubleshooting inter process communication

I have output captured by following command: strace -f -e trace=process,socketpair,open,close,dup,dup2,read,write -o rsync.log rsync -avcz --progress src/ dst/ it is a bit long so I've uploaded it ...
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0answers
24 views

Ensure that file socket is already opened

I'd like to open a simple file socket that can run in background like: nc -l -k -m 10 -U my_socket -c cat & so other processes can connect into it with nc -U my_socket -c read. After this ...
1
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1answer
32 views

How to bind (or remap) a socket with an abstract name to a path?

In our system (Linux 4.4) we see a a unix socket with an abstract namespace (those starting with @ with no corresponding file on the file system). Showing its details with lsof reports: serv 7539 ...
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0answers
20 views

PAM: make dbus listen to some address

I'm new with PAM and have some questions about it. Is possible to make PAM configure dbus, and make dbus listen to some address?
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1answer
82 views

Udev rule setting up SocketCAN socket only works correctly only when run manually

I want to start slcand (the userspace daemon for the serial line CAN interface driver) when my Lawicel CanUSB dongle is plugged in. I followed Pascal Walter's step-by-step guide and all seems to work (...
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0answers
26 views

Socket timeout from an upstream DNS server nxfilter [closed]

We are using ubuntu 14.04 server and installed nxfilter latest version. After the run ./startup.sh script file, getting below error after the 2-3 minute and If i stop and start the again script then ...
1
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0answers
150 views

Unable to start apache

I'm running CentOS7 in virtualbox on a mac (osx 10.9.3). Ultimately, I want to access the website on my Guest VM from my Host. I can Ping and SSH to VM but I can't access the webpage when entering ...
2
votes
1answer
89 views

why do I find (under /proc/pid//fd) sockets with broken symlinks

I don't think they're closed, because I would expect that after a close() the fd would disappear, but I see a bunch of lingering fd -> socket[xxxxx] entries with broken symlinks which don't seem to be ...
3
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0answers
85 views

Read but not write access to a socket on Linux, what can one do with that?

On a server installation, I found sockets writable by group, but only readable by others. I assume that the latter has no effect, as my understanding was that write access is needed to be able to work ...
2
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1answer
1k views

Linux nuisance: /dev/stdin doesn't work with sockets

Linux has this blitheringly annoying peculiarity that /dev/stdin won't work with sockets - it is hardcoded to return ENXIO. Try this: socat TCP-OPEN:localhost:1234 EXEC:cat\ /dev/stdin,nofork That'...
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3answers
19k views

ssh: Read from socket failed: Connection reset by peer

When I try to ssh to a remote host, I get the following error messages: root@cloudstack-server-1:~/.ssh# ssh ubuntu@172.17.4.17 -v OpenSSH_5.9p1 Debian-5ubuntu1.1, OpenSSL 1.0.1 14 Mar 2012 ...
2
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1answer
79 views

Blocking a specific external IP:Port connection in RedHat?

I know that in RedHat, in the IP tables I can block incoming connections to a local port. I can also block connections from a specific IP. But is it possible to block a connection from a specific IP ...
1
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0answers
17 views

Several TCP Window Scale values depending on interface?

Is it possible that TCP Window Scale value set by default on a socket (not raw) depends on the interface used? Where are these values stored?
5
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0answers
622 views

OEL6 Slow boot && Millions of socket files in /tmp/orbit-gdm

Background on question Lately I've been having some trouble with slow booting on the servers, sometimes over 2 hours to boot stuck on "Enabling Local Filesystem Quotas:" After searching I managed to ...
1
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1answer
34 views

How do I get active unix domain sockets for a specific pid if I can't use lsof command?

If I have no permission to use lsof, how do I get them for a process with pid already known? Thanks I know netstat -l -p command print out active unix domain sockets, but it seems it's not updating ? ...
1
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1answer
131 views

How to pass received data from netcat to another script as argument?

I have simple bash nc script: #!/bin/bash nc -k -l 127.0.0.1 4444 > filename.out which listens 4444 port for TCP connection. Instead of redirecting received data to filename.out I would like, if ...
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6answers
10k views

What is a socket?

Could someone explain to me what a socket is? I see it in many acronyms in context of SSL, etc. Also, why is it called a socket? Is it purely because it was what a name they invented? Or was it the ...
11
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1answer
687 views

Does Linux automatically clean up abstract domain sockets?

There's a great answer on StackOverflow about providing a better lock for daemons (synthesized from Eduardo Fleury) that doesn't depend on the common PID file lock mechanism for daemons. There are ...
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0answers
27 views

Implications of increasing igmp_max_memberships

I am writing an application that will subscribe to 150+ multicast groups. It appears the linux default number of multicast subscriptions is 20 which can be increased via sysctl -w net.ipv4....
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1answer
49 views

Where to put socket so PrivateTmp can be true

I have a C++ program which must communicate with other services (including httpd), and does so via a socket in /tmp With the advent of systemd and the PrivateTmp=true setting, processes like httpd ...
2
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0answers
154 views

Netlink access inside a network namespace

I'm trying set up an IPsec gateway (strongSwan) on a Raspberry Pi 2. The Pi was already providing a number of services on the LAN using a private IP address. My initial attempt to turn it into an ...
1
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2answers
10k views

Could not bind socket: Permission denied when trying to start NDOUtils using UNIX socket

I followed these directions to a tee: http://shah-oss.blogspot.com/2010/12/ndoutils-installation-on-centos-for.html Everything was going well until I actually tried to run this command (there is a ...
3
votes
0answers
131 views

Sharing unix sockets across unprivileged lxcontainers

I have two unprivileged containers and I'd like to share a unix socket between them. Each container has its own user on the host, complete with separate subuid and subguid mappings. I've tried ...
3
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0answers
13 views

Limit access/transmit rights on NIC to a single user application

I currently have a RT patched linux machine and I need to have full and undelayed access to my Wired interface card. I am running a realtime non-preemtable user application which sends a couple of ...
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0answers
86 views

espeak, alsa Unknown PCM

I have a Debian Wheezy and I connected to my linux a USB Dac. I use every time a MPD server (and that work) Now, I would like to use espeak with pyttsx But when I start my script (It worked and my ...
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0answers
39 views

How to decrypt data buffer in kernel level before read/recv [closed]

Before reading contents from socket file descriptor using read/recv(), can we preprocess/modify(e.g. decryption) data buffered in kernel level? I have server&client programs written in C, and I ...
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2answers
89 views

shell command wrapper for socat

I have used the command socat - foo The text I type is sent directly to address foo. Is there some general-purpose wrapper for stdin (along the lines of ! from ed) that lets one parse a shell ...
2
votes
1answer
67 views

When is a port considered being used?

I am getting port in use cannot bind on process restarts. I am trying to find out when a port is considered being used? Is it only when in LISTEN mode? Can it also be if a connection is open to the ...
1
vote
1answer
132 views

Socket remains ESTABLISHED even if remote process is stopped

I am running a celery - rabbitmq configuration between a client and a server. The client process opens a connection on the server at port 5672. Using netstat -np on the server I confirm that since the ...
11
votes
2answers
217 views

What is the difference between &6 and /dev/fd/6?

To read from file descriptor 6 I can use <&6 or </dev/fd/6 (aka /proc/self/fd/6). Usually both work equally well. However if that file descriptor happens to be a socket, strange things ...
1
vote
1answer
92 views

How to provoke a broken pipe

I try to debug a python script that interfaces MPD using python-mpd2. When the script tries to perform an action after being idle for a couple of hours, it terminates with an exception (...
3
votes
1answer
113 views

root cannot connect to symlinked socket of other user

I use oh-my-zsh's ssh-agent plugin to have a static symlink to my current SSH_AUTH_SOCK created. When connecting through SSH with agent forwarding enabled the file /tmp/ssh-agent-$USER-screen is ...
5
votes
2answers
4k views

How to send data from serial port over wifi?

I have microcontroller device which reads data from sensors and sends it via Serial to USB converter (ftdi232 cable). This Serial to USB converter is connected to ARMv7 mini-computer - CuBox with ...
2
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0answers
57 views

how to list all the epoll requests in linux

I used to use netstat for displaying all listening sockets. How can we list epoll requests on the sockets? Or is there anyway to dislay epoll requests using netstat?
1
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1answer
229 views

/private/var socket not created with postfix/dovecot sasl

I'm currently running into a problem I have with my email server. I try to setup Postfix and Dovecot with SASL authentication but I get the following error when I connect with telnet (port 25) to the ...
30
votes
6answers
10k views

Who's got the other end of this unix socketpair?

I want to determine which process has the other end of a UNIX socket. Specifically, I'm asking about one that was created with socketpair(), though the problem is the same for any UNIX socket. I ...
2
votes
1answer
96 views

Time synchronization, use NTP or just socket?

I am using a PC and a raspberry pi(both run Linux) to gather sensor data, raspberry pi gathers laser scan data, PC gathers image captured by camera. I must synchronize time for these two machines. I ...
0
votes
1answer
41 views

strace vs web browser

I was trying to strace an iceweasel like this: strace -e trace=connect iceweasel And I was expecting to see calls to connect when I load new pages. Surprisingly, there weren't any. Why so? Am I ...
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0answers
39 views

Connection refused, but only on one specific port

I have two service daemons. One responds; the other does not. The command netstat -pln returns, among others, Proto Recv-Q Send-Q Local Address Foreign Address State PID/...
0
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1answer
32 views

Server port doenst go back to listen and is in closed_wait state , because of starting an daemon application from client

Below is the basic client and server code . While iam trying to start an appliaction(which has to keep running in the machine once we send a msg to server) during connect call. using system(/bin/...
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1answer
358 views

How to get more info about socket file?

For a socket file likes this: # ls -alti socket 14112 srw------- 1 root root 0 Nov 15 20:03 socket # cat socket cat: socket: No such device or address Since cat command is useless here, is there ...
14
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4answers
12k views

Are FIFO, pipe & Unix domain socket the same thing in Linux kernel?

I heard that FIFOs are named pipes. And they have exactly the same semantics. On the other hand, I think Unix domain socket is quite similar to pipe (although I've never made use of it). So I wonder ...
2
votes
1answer
237 views

Differences between Unix Domain Sockets and Network Sockets?

Am I right that When two processes communicate by network sockets, each process create a socket (each socket belongs to one process), and the processes communicate by their sockets. When two ...