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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1answer
963 views

Memcache 'stats' reports non-zero 'curr_connections' - but lsof shows no socket connections

Our memcache daemon reports non-zero 'curr_connections'... $ telnet memcache-server 11211 Escape character is '^]'. stats ... STAT curr_connections 12 ... ...and yet, lsof shows no socket ...
8
votes
3answers
2k views

Is there a file for each socket?

"Everything is a file" in the UNIX World. Above sentence is famous. When I run echo "hello programmer" >> /dev/tty1 , I can watch the given string on TeleType 1 , .... What and where is file ...
2
votes
2answers
130 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 ...
1
vote
2answers
191 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 ...
3
votes
2answers
1k views

Socket connect to a ports bound to IP vs localhost

It is my understanding that sockets bound to ports using localhost will not be visible to the subnet because the binding is not with the nic IP address. Local processes connecting to such port will ...
2
votes
1answer
571 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 ...
1
vote
0answers
329 views

Which socket is gnome-shell reading from continuously?

strace shows that the GNOME shell is continuously trying to read from a socket, which is often not available (or doesn't contain any data to read from): strace -p gnome-shell-pid -e trace=recvfrom ...
3
votes
1answer
81 views

= sign at the end of .sock files in the ls output

I'm running the zsh shell in emacs. When I run ls I get a = at the end of .sock files. What does the = mean? Is it unique to unix sockets?
1
vote
2answers
938 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 ...
4
votes
1answer
122 views

Does traffic addressed to one of a Linux system's own interfaces ever leave the system?

I have two separate servers running on the same port on a Linux system, one binded to the loopback interface, and the other to the public Ethernet interface. If I connect a client on that system to ...
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 ...
4
votes
5answers
18k views

How can I tell if a TCP port is open or not? [closed]

I am trying to implement socket programming in C. When I try to connect from a client to a server (Ubuntu), it shows an error like "connection failed". So I think the problem is with the port. I am ...
9
votes
1answer
276 views

Can someone explain the different types of unix domain sockets?

If I run netstat --all | grep ^unix some of the socket paths that are outputted are preceded with a '@' and some aren't. I've noticed that those preceded with a '@' don't show up when browsing the ...
14
votes
2answers
10k views

Performance of unix sockets vs TCP ports

For example on php-fpm: #listen = 127.0.0.1:9000 listen = /var/run/php-fpm/php-fpm.sock Is there any major performance differences between using unix socket-based listeners over TCP ports? (Not ...
3
votes
1answer
2k views

How to 'free' a TCP port?

I have some code that listens to a specific TCP port. However, when I stop this code and restart it quickly afterwards, I see the error ERROR: could not bind to socket on 0.0.0.0:7700 If I wait a ...
5
votes
1answer
879 views

Idiomatic location for file based sockets on Debian systems

I am writing a daemon process for a Debian system in C that uses a Unix Domain Socket. If the deamon process's working directory is the root directory, is there an idiomatic directory to place the ...
3
votes
2answers
679 views

Which systems do not honor socket read/write permissions?

man 7 unix on Linux states: In the Linux implementation, sockets which are visible in the file system honor the permissions of the directory they are in. Their owner, group and their ...
4
votes
2answers
4k views

How to 'strace' a unix domain socket?

Kind of hard to explain but I noticed when straceing the PID that has the socket open I cannot see any of the communication. How can I sit in the middle of a socket file to watch communication?
1
vote
1answer
6k 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 ...
2
votes
1answer
974 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 ...
11
votes
4answers
8k 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 ...
6
votes
4answers
9k views

How does the server find out what client port to send to?

As I understand it this is what happens when a client makes a connection request: The server will be bound to a particular port number. The port number is always bound to a listening process. Since ...
4
votes
2answers
801 views

Cross-process dup on Linux

I'd like to dup a file descriptor running in an unrelated process on Linux. I know about sendmsg(2) and SCM_RIGHTS (e.g. ...
0
votes
2answers
113 views

Why flipping is done on data from Big endian before storing in LE?

Simple but confusing question for a beginner. Suppose A is a BE machine and is sending 0x44332211 sending data to B which is LE. By default A will be using htonl of 0x44332211 which is nothing but ...
0
votes
1answer
1k views

How to connect to port immedeately, avoiding socket_bind(): unable to bind address?

When running a code that is supposed to read from a TCP/IP port I often get the following message (depending exactly what language have been used): socket_bind(): unable to bind address I know that ...
1
vote
1answer
156 views

Communication to device is lost when network starts on boot up?

I have an application that opens a socket on port 4444 to a device (/dev/linkToDevice). The "linkToDevice" is a link to ttyUSB0. The application is a c++ program of which is now a daemon and runs at ...
2
votes
1answer
85 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 ...
-1
votes
3answers
681 views

telnet implementation using C [closed]

The program in general is I want to implement telnet program. On the client side user send its logging name and password, and if it is correct he starts to send commands to the server On the Server ...
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... ...
0
votes
2answers
310 views

Physical layer header is not present in the data read from raw sockets?

i have read about RAW sockets that they are UNIX domain sockets and don't generally go over the wire unlike TCP or UDP. They are used for interprocess communication. Also they are used in the ...
5
votes
1answer
446 views

In bash, can I asynchronously open sockets and use them later?

I had no idea that Bash supported so many advanced features! I started working on a simple network program to try and use some of these things I found. My particular program is a basic redis client ...
2
votes
0answers
269 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 ...
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 ...
2
votes
0answers
246 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 ...
0
votes
1answer
812 views

pcap and raw socket [closed]

I want to develop an application (module or user-level if possible) to create a raw socket in RHEL stealing all level-2 packets directly from kernel (without being routed or handled by other open ...
1
vote
0answers
1k views

Symbolic link to a socket

From a security point of view, is it safe to create a symbolic link to a socket file? The following bits of context refer to the deployment of a web application on a shared hosting service. $ ls -al ...
2
votes
1answer
3k 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 ...
1
vote
1answer
1k views

Where to locate “sockets”

I am new to this, so sorry if its obvious. I am running a Debian server and installing the likes of UWSGI, NGinx etc on there. The configurations keep talking about pointing to "sockets". In the ...
3
votes
1answer
1k views

Closing socket connection on running console application

I am testing a chat bot and want to gracefully handle for times when the chat server isn't running so it can come back up when the service is available again. I have the programming handled. My ...
4
votes
2answers
7k views

File descriptor linked to socket or pipe in proc [duplicate]

Possible Duplicate: /proc/PID/fd/X link number i have a question regarding the file descriptors and their linkage in the proc file system. I've observed that if i list the file descriptors ...
1
vote
1answer
828 views

Netstat shows programs running on different ports then they should

I have some code I'm testing. Program A listens on a predefined socket for program B to connect to and for my testing I'm running 32 instances of the programs A and B. I've written my script to tell ...
0
votes
2answers
1k views

Force getaddrinfo to use IPv4

The man page says: The getaddrinfo(3) function is not limited to creating IPv4 socket address structures; IPv6 socket address structures can be created if IPv6 support is available. These ...
2
votes
1answer
235 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: ...
3
votes
1answer
5k views

Kill TIME_WAIT sockets immediately?

Is there anyway to kill those TIME_WAIT sockets immediately ? e.g output of netstat: tcp 0 0 127.0.0.1:8080 127.0.0.1:41500 TIME_WAIT - tcp 0 ...
2
votes
2answers
3k 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 ...
3
votes
1answer
441 views

User associated with a socket

I use ss -p to see TCP sockets information. But process info are not printed for some sockets. Below: $ ss -p4 State Recv-Q Send-Q Local Address:Port Peer Address:Port ESTAB 0 0 ...
1
vote
1answer
418 views

How to limit all tcp traffic to the network interface the session was initiated on?

I have an embedded linux system with two network interfaces (lan0, wlan0) that are configured to the same subnet. A server on this system accepts tcp connections on both interfaces. How I can assure ...
2
votes
0answers
404 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 ...
5
votes
2answers
4k views

Write inside a socket open by another process in Linux

Is it possible on Linux for a process to write inside a socket open by another one? Let's say I open a connection to google.com using netcat: myuser@linux:~$ nc google.com 80 Now I can lookup for ...
13
votes
1answer
2k views

Kernel socket structure and TCP_DIAG

I'm working on a software which connects to a Real Time data server (using TCP) and I have some connections dropping. My guess is that the clients do not read the data coming from the server fast ...