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

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3
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0answers
347 views

How do you write test cases for a web server that uses posix sockets? [closed]

I know how to test it experimentally by running the program, but ideally I would like to test each function I write as I write it. Usually I can't test my functions until I write a whole bunch of ...
2
votes
1answer
86 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 ...
2
votes
1answer
54 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 ...
2
votes
1answer
49 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 ...
2
votes
1answer
96 views

Custom application running on embedded device - do I need to register my listening port in /etc/services?

I have written an application that will run on an embedded device. The installation is very minimal and uses busybox and not many other things. Part of the software includes a listener thread that ...
2
votes
2answers
4k views

Size of data that can be written to / read from sockets

I was wondering if there is an easy way to find the maximum size that is supported by Linux sockets? (Is this configurable? If so where?) For example, most of the socket examples found on the web ...
2
votes
2answers
173 views

Detect open sockets manually (not using nc or similar)?

I'm trying to debug a network problem on a embedded system which has a very limited set of userspace applications. Meaning I can't use any of the following sudo lsof -i sudo netstat -lptu sudo ...
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 ...
2
votes
1answer
2k views

Why can't I use strace with rsh?

If I run rsh, it works, but prints some strange “Connection refused” messages at the beginning: $ rsh localhost pwd connect to address 127.0.0.1 port 544: Connection refused Trying krb4 rsh... ...
2
votes
1answer
5k views

Adjusting rsync TCP timeout

I'm using rsync in my own C++ program by issueing the command system("rsync -rauzvq root@host:/folder"); I use this for keeping multiple systems in sync. Now I have the problem that when a remote ...
2
votes
1answer
511 views

How to report receive queue size for AF_UNIX sockets

netstat -a reports Recv-Q (amount of unread data pending for a reading application) for AF_INET sockets, but not AF_UNIX sockets (at least not for SOCK_DGRAM). Does anybody know a way to obtain this ...
2
votes
1answer
250 views

Why does this simple Perl client not work?

I am fairly new to IPC with sockets and expect this issue is a simple one to resolve. I'm trying to understand why I cannot get this example script from perldoc perlipc to run on my Ubuntu setup: ...
2
votes
1answer
30 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 ...
2
votes
1answer
105 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] ...
2
votes
1answer
127 views

using a pty like a socket?

I'm writing a collection of scripts to talk to an external program. My problem is that the scripts are only "alive" for a short time (triggered by a keypress in a larger program) but the external ...
2
votes
2answers
6k 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 ...
2
votes
1answer
484 views

Advantages of using named pipes and sockets rather than temporary files

I have two cooperating programs. One program just writes its output to a file and the other one then reads from the file and spits the data out for the front end to work with. I have been reading ...
2
votes
1answer
957 views

Using a Unix Domain Socket to Control VLC

I am interested in using a UNIX-Domain Socket to control VLC playback. This functionality is outlined in the VideoLan documentation for using oldrc. So what I need to is startup vlc with a command ...
2
votes
1answer
1k views

Espeak showing some warnings and Input output error

I am running espeak on Linux Mint 14. Whenever I try to run it, it shows following warnings ( Not errors as it works correctly ). ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM ...
2
votes
1answer
192 views

Wrapping socket connections

I'd like to wrap an insecure connection (this one: http://culturedcode.com/things/) with a secure tunnel, a bit like http://en.wikipedia.org/wiki/Stunnel does, just using UNIX tools. What's the best ...
2
votes
1answer
179 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 ...
2
votes
1answer
508 views

Connect through different interfaces to the same server (SO_BINDTODEVICE): Destination Host Unreachable

I have 2 interfaces: eth0 and wlan0, each one connected to a different router. Their network specs are these: eth0: ip: 192.168.1.7 Gateway: 192.168.1.1 Submask: 255.255.255.0 wlan0: ...
2
votes
0answers
45 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
0answers
240 views

What does an inode for a socket contain?

I read somewhere that the inode for a TCP socket would contain the buffer space. Is that true, and if so, does it mean that the inode contains a memory address for the buffer space used by the ...
2
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0answers
46 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 ...
2
votes
3answers
1k views

Nginx leaves old socket

I'm running Nginx 1.6.2 (the nginx-full package from the nginx/stable PPA). I'm using the unmodified configuration /etc/nginx/nginx.conf: user www-data; worker_processes 4; pid /run/nginx.pid; ...
2
votes
0answers
204 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
votes
0answers
683 views

X11 bad access at first try but working on successive tries

I use the following setup to forward X11 output from my local machine to the server. I will outline the setup: X11 server and the client are on the same local machine. The X11 server runs on my ...
2
votes
1answer
147 views

Is there a system call to bind a file descriptor directly into another?

A read() & write() loop would probably be as good as what I'm looking for, but nevertheless is anything like that around or is it impossible because of an obstacle I didn't envisage ? I'm curious
2
votes
0answers
92 views

Last data traffic time for a TCP socket

Is it possible, to find out when was the last time there was any traffic on an opened TCP socket? Keepalive and timeout timers are based on this statistic, so I guess it has to be stored somewhere. ...
2
votes
0answers
270 views

Best location and permissions for socket files [duplicate]

I will have a couple of WSGI applications. They will communicate with nginx using sockets. For that purpose I've created the directory /run/wsgi in which I will place all the socket files that are ...
2
votes
0answers
495 views

Does epoll give available bytes to read or write, and threshold feature?

kqueue gives available bytes to send or receive if file descriptior (such as socket) gets signal. and, kqueue gives threshold feature, for example, it does not signal until sufficient bytes are ...
1
vote
1answer
574 views

How can I allow applications to bind to any address in a subnet assigned to an interface?

I recently got a static IPv6 /56 prefix of my own from Freenet6, and am trying to allow applications to bind arbitrary addresses in the prefix. I modified the tunnel creation script that gogoc uses in ...
1
vote
2answers
2k views

How to “listen” to nginx writes to a file socket

I'm trying to get uwsgi and nginx to play nice. After moving to "file sockets" (hopefully I'm using the right terminology here) from TCP sockets, the only thing I get from uwsgi is a 400 with no ...
1
vote
1answer
70 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 ...
1
vote
1answer
207 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 ...
1
vote
2answers
397 views

Runs perfectly through the command line, will not work through systemd ExecStart

I've installed Butterfly http terminal server, written in python, on my Arch machine. I'm new to systemd, but I'm having an issue with one of the command line parameters. /usr/bin/butterfly.server.py ...
1
vote
3answers
885 views

nc not waiting for server disconnect on OS X

How to make nc client on OS X Mavericks keep socket open and read data until server disconnects the socket? I want to send data to a server through nc and then use the response. Problem is that nc ...
1
vote
2answers
407 views

How to see the amount of pending data on a unix domain socket?

When I'm logged to a tmux session from two different computers, I'd like to be able to trace the amount of pending data on the sockets of both tmux session. To test this I logged to computer A and to ...
1
vote
1answer
78 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 ...
1
vote
1answer
229 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 ...
1
vote
1answer
21 views

What setsockopts() 'name' values are used by the running Linux kernel?

I am introducing some new socket commands with nf_register_sockopt(&my_new_socket_options). How can I find, what setsockopt commands are already used (registered?) by the currently running kernel, ...
1
vote
1answer
660 views

ss is replacing netstat, how can I get it to list ports similarly to what I am used to?

I've been trying to modernise my way with Linux by, for one thing, ditching netstat for ss. I looked up my favourite command line flag for netstat in the ss man pages, and was very glad to find that ...
1
vote
1answer
285 views

ip forwarding to remotely connect to a socket listening to localhost only?

I must transfer data from PC1 to PC2 using a specific port, but the socket opened on PC2 only listens to local host. Is there a way to "trick" the socket into accepting the connection from PC1?
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 ...
1
vote
1answer
1k views

Default value for SO_RCVTIMEO option on Solaris

Is there any way to find out what is the default value set for option SO_RCVTIMEO on Solaris 10? If there is a way to find out how would one go about changing it? P.S. I am aware of ability of ...
1
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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?
1
vote
1answer
27 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
65 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 ...
1
vote
0answers
19 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 ...