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

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2
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1answer
21 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
votes
0answers
60 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
votes
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 ...
0
votes
0answers
8 views

SocketCAN read socket call is blocking [migrated]

I am trying to do a socket read from CAN socket. My read call is getting blocked and never returns control outside. Steps in my code flow: open a socket assign interface name assign CAN ID Assign ...
3
votes
3answers
17k 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
votes
1answer
38 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
vote
0answers
17 views

what can cause a socket() “Permission denied” error? [migrated]

Under Android 4, the following simple native C code line fails with an Permission denied error when not run as root: online_socket = socket(AF_INET, SOCK_DGRAM, 0); I do have root access to the ...
1
vote
0answers
14 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?
4
votes
0answers
402 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
vote
1answer
22 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
vote
1answer
52 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 ...
20
votes
6answers
8k 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
votes
1answer
498 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 ...
1
vote
0answers
17 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 ...
1
vote
1answer
24 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 ...
1
vote
0answers
66 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
vote
2answers
9k 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
59 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
votes
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 ...
0
votes
0answers
54 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 ...
1
vote
0answers
23 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 ...
-1
votes
2answers
41 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
40 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
62 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
165 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
64 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
74 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
3k 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
votes
0answers
42 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?
2
votes
2answers
5k 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 ...
1
vote
1answer
211 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
9k 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
79 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
34 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 ...
0
votes
0answers
31 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 ...
0
votes
1answer
29 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 ...
1
vote
1answer
186 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 ...
12
votes
4answers
11k 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
159 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 ...
0
votes
0answers
38 views

What kinds of IPC are used in ssh port forwarding?

SSH local forwarding is specified by: -L [bind_address:]port:host:hostport on the local host, a process called P1 attaches to port, so that P1 and the ssh client SC can communicate. What type of ...
0
votes
1answer
40 views

What's the relationship between SOCKS and socket?

SOCKS (socket secure) is a protocol for proxy. A socket is an endpoint of communication. Why is SOCKS named after socket? How are they related?
2
votes
1answer
95 views

How do I find out more about socket files in /proc/fd?

Looking in /proc/$mypid/fd/, I see these files lrwx------ 1 cm_user cm_user 64 Oct 14 03:21 0 -> /dev/pts/36 (deleted) lrwx------ 1 cm_user cm_user 64 Oct 14 03:21 3 -> socket:[1424055856] ...
1
vote
1answer
193 views

Is it possible to establish a Socket session (between Server and Client) using shell commands ?

From what I read (only the very outline, i do not know C Language) a Socket session is established between a server and a client by calling functions for both of them in a certain order. It starts ...
0
votes
0answers
55 views

How to view source service(Process Name), when connection is established

Imagine there are 3 servers server1 has Haproxy, server2 has apache and server3 has MySQL. Deployed an application in server2. Client can send the request via Haproxy to server2. Apache listens on the ...
12
votes
3answers
21k 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 ...
3
votes
0answers
211 views

Scripted write-then-read from Unix domain socket using socat

I have a simple server listening on a Unix domain socket (on a CentOS box in case that's important). When I send the command "DATE" to the socket it writes back a welcome message and then "APRIL 15 ...
1
vote
0answers
48 views

What does the “ss -s” result “Total:” value represent? How to get details on each of them?

I am trying to understand what the ss -s result line Total: value represents, along with how this number is related to the other numbers. Note, the following values are equivalent: ss -s Total: == ...
3
votes
2answers
304 views

Distinguish TCP server from client within netstat output

I have a socket connection between a client process and a server process, both running on my machine. There are two entries shown for the connection as, sudo netstat -ntp | grep 56442 tcp 1 ...
0
votes
1answer
58 views

Is the return value “-1” of the function socket close() method possible?

Under which circumstances is it possible to produce a return value of -1 when closing a network socket using it's close(int fildesc) method? I suppose it is possible with an invalid fildesc number, ...
-1
votes
2answers
239 views

Free or cheap shell (i.e., platform) to run a Linux C program with root privileges (raw socket)

I'm working on a Linux C program that needs root privileges (raw socket). I would like to run it on a host located in the US (I am in EU) to compare results. Is there any free (or cheap) shell ...