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

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29
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6answers
8k 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 ...
21
votes
2answers
13k views

/proc/PID/fd/X link number

In Linux, in /proc/PID/fd/X, the links for file descriptors that are pipes or sockets have a number, like: l-wx------ 1 user user 64 Mar 24 00:05 1 -> pipe:[6839] l-wx------ 1 user user 64 Mar 24 ...
20
votes
5answers
7k 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 ...
6
votes
2answers
12k views

rpc.statd running on system not using NFS

I have a Debian machine that gets warnings (via the Tiger automatic auditor) that rcp.statd is listening on such-and-such socket. Googling shows rpc.statd is a daemon used by NFS. As far as I know, ...
6
votes
2answers
5k 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 ...
12
votes
3answers
19k 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 ...
20
votes
4answers
1k views

Are Unix Internet sockets files?

I understand that "Everything is a file" is one of the major concepts of Unix, but sockets use different APIs that are provided by the kernel (like socket, sendto, recv, etc.), not like normal file ...
11
votes
4answers
10k 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 ...
4
votes
1answer
149 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
403 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
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 ...
3
votes
2answers
227 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 ...
3
votes
2answers
997 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 ...
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... ...
1
vote
2answers
325 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
2k 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 ...
0
votes
0answers
28 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 ...