Questions tagged [unix-sockets]

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Unix-domain Socket

I'm trying to set my server up and came across some troubles related to Unix domain sockets. I don't have so much experience with Unix, despite the stack for web development: Apache, PHP and SQL. I ...
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What does SCM mean in unix sockets context (SCM_RIGHTS etc.)?

From man 7 unix SCM_RIGHTS Send or receive a set of open file descriptors from another process. The data portion contains an integer array of the file descriptors. The passed file descriptors ...
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umask ACLs and socket permissions

I looked at the answer here How to set default file permissions for all folders/files in a directory? And set the acls using setfacl getfacl: Removing leading '/' from absolute path names # file: run/...
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How to allow the docker container to reach host's X11 socket without --net=host?

The old trick, using '-v /tmp/.X11-unix:/tmp/.X11-unix' to allow to use the host container no longer works. I could make it work using '--net=host', but that makes the guest use the whole net ...
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How to create a .sock file for unix_stream

I am new to this socket programming in linux I want to send a log file i.e eve.json This file is provided by suricata and they have already defined some setting in their configuration yaml to send ...
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Do unix domain sockets support reuse?

Do unix domain sockets support reuse? Lots of conflicting information about this online. I suspect a lot of it is just outdated, but I'm no expert. Do I ProxySet enablereuse=on if my handler is a ...
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Interacting with Unix Socket found in lsof

I found a Unix socket being used in the output of the lsof command: COMMAND PID TID TASKCMD USER FD TYPE DEVICE SIZE/OFF NODE NAME screen 110970 ...
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How can I guess server socket type

I try to connect to my UNIX-socket server using openbsd-netcat, but have an error: connect(): Protocol wrong type for socket My socket type is SOCK_SEQPACKET, and it seems that nc tries to open it as ...
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Why does socat fail at proxying X11 where ssh succeeds?

I am investigating how to write a simple X11 unix-socket-based proxy. I have tried various standard applications, as well as written my own code, but I am getting wildly variable results. What's ...
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How can I target an X window to a secondary monitor? (and know what it is called in order to do that)

I have two monitors connected (one HDMI, one DVI) connected to an Nvidia GT710 GPU on my linux box. When I am logged in to my box over ssh, if I run xeyes it will always run on the same screen. I ...
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unix domain socket permissions and umask integration between root and non root users

I'm trying to understand the permissions of a unix domain socket, when using an existing file, umask changes are required as well as the dir permissions. If I create a world readable dir as root and ...
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How to listen the requests sent to a unix socket

I'm learning docker and wanted to see the API commands sent by the client to the docker server/engine. I know that the communication between the two processes happens via /var/run/docker.sock. Is ...
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What does 'Reached target Sockets' mean and what are possible fixes?

I have golang web application which runs by systemd daemon in a Debian Server. I've noticed that sometimes myapp stops while I see a message like this in syslog: Aug 20 07:34:20 myapp systemd[29414]: ...
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apt-daily.service seems to interfere with Unix sockets

We have an embedded device with Debian 9 that has been running for over a year without issues until recently. We have a process that acts as an aggregator and communicates every second with several ...
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"Holding" a socket open too long causes a new one to spawn

I am connecting to a socket via nc -U: user@node:~$ sudo nc -U service\@name.18822.sock user@node:~$ xmpp.status user@node:~$ connected If I "hold" this connection open too long, it will ...
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Problem Accessing UNIX sockets remotely via SSH tunnel

I'm trying to use a TCP port to connect to a MySQL unix domain socket on a remote machine. I have removed networking on the mySQL server to harden it. The SSH tunnel looks like this: MyPC <---------...
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Possible scenarios for Unix domain sockets interruption

When using TCP & UDP sockets, there are many scenarios which cause connection interruption (slow connection, network reset, etc). Is there any possible situation which an unix domain socket ...
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How can I use GPG agent forwarding over ssh when systemd owns the remote sockets?

I'm trying to follow these guides and answers https://wiki.gnupg.org/AgentForwarding https://superuser.com/questions/161973/how-can-i-forward-a-gpg-key-via-ssh-agent https://gist.github.com/...
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socat bidrectionally with a shell script. echo, read, then hand off to socat

There is a VMM which doesn't conform to the the standard VSOCK implementation: Firecracker For each guest it creates a v.sock unix socket file The ordinary VSOCK-CONNECT:cid:1234 then becomes: UNIX-...
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AF_UNIX: Using recv() to receive a message sent with sendmsg()

The function prototype for the sendmsg() function is as follows: ssize_t sendmsg(int sockfd, const struct msghdr *msg, int flags); and the msghdr struct is such: struct msghdr { void *...
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Why systemd says it's dependency system should be used only sparingly?

From systemd.unit(5) man page: Note that while systemd offers a flexible dependency system between units it is recommended to use this functionality only sparingly and instead rely on techniques such ...
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hostnamectl command causes Failed to create bus connection: No such file or directory

I'm following this guide and I'm running into issues. https://www.tecmint.com/initial-ubuntu-server-setup-guide/ I am trying to create a linux machine in Ubuntu in wsl2 and then rename it using ...
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How to use unix domain socket for tor socks

I am trying to setup a unix socks socket for tor usage instead of port 9050 in the hopes to gain a tiny bit of performance. However I am getting the below error: Oct 21 11:53:54 HOSTNAME Tor[992986]: ...
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What happens when two processes listen on the same Berkeley/Unix [file] socket?

What happens when I set up two processes to listen to the same Berkeley socket? Do messages get routed to both? Neither? One of the two? If so, how? Concretely, I can start two gunicorn processes with ...
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/proc/[pid]/fd/[0, 1, 2]: No such file or device - even though file exists

I'm trying to access a process' stdio streams from outside its parent process. I've found the /proc/[pid]/fd directory, but when I try $ cat /proc/[pid]/fd/1 I get a No such file or device error. I ...
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Can systemd be used as an inetd/xinetd replacement without being an init?

Can systemd be configured (in runtime or compile time) to serve as a simple process supervisor, not as /sbin/init? If yes, are there tutorials and other documentation to follow to make customized non-...
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Does every socket have its own buffers to send/receive messages?

I'm developping a C application that make extensive use of sockets. My doubt is: Does every socket that I create have its own buffers to send and/or receive messages from other sockets? In other words,...
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what will happen if receiver unable to handle data velocity through socket?

I have two processes P1 (sender) and P2 (receiver). P1 uses unix-domain-socket (UDS) to send data to P2. what will happen if P1 sends data at the rate of 100 messages/second and P2 is capable to ...
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Is there a command to list all abstract unix sockets currently open?

Is there a command or system call for listing all the abstract unix sockets currently open? Update: It was suggested that I use netstat -x, which theoretically works, but does not list the names of ...
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Are socketpairs useable as signal-safe buffers?

I am thinking on a way of communication between signal handlers and the main program. Note, I use mosly non-blocking signals (a new signal can arrive even while a signal handler is executed), so I am ...
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1 vote
1 answer
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Stop child services when systemd socket connection closes

I'm trying to launch a meta-service remotely through a socket. Requirements: The socket should start the meta-service when a connection is established The meta-service should start all child (Wants=)...
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1 vote
1 answer
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How to get notified when the other end of a socketpair is closed?

I have a parent process (client) talking with a child process (server) over Unix Domain sockets (aka IPC Sockets). The sockets are created using socketpair() and are of type datagram. I use ...
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4 votes
2 answers
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Unix domain sockets for non-root user

I work on the application that uses Unix domain socket for IPC. The common way as I know is to place the socket file inside /var/run. I work with Ubuntu 18.04 and I see that var/run is a symlink for /...
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6 votes
1 answer
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Display webpage with unix domain socket

Is there a way to serve a webpage from a locally running tcp server listening on a unix domain socket instead of localhost:<port>? something like: file:///tmp/webpage.sock my only real ...
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cannot find screen session I detached from

I am running a program on Unix server and I am mindful that I detached the screen and logged out of the server. Later I ssh'd back in and tried to reattach but I just cannot find my screen. In fact ...
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Connect docker-container with other container by unit-socket

I'am trying to connect to containers by unit-socket/ docker run -d -v /var/lib/docker/overlay/[container_id]/var/run/postgresql/.s.PGSQL.5432:/socket_volume/.s.PGSQL.5432 -p 50000:8080 my_repo/...
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3 votes
1 answer
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Binding a AF_UNIX to any existing file?

Can we bind a Unix domain socket to any random existing file ? If no, how do you recognize a file that is used by a socket ?
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2 votes
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Security issues for passing credentials over a UNIX socket

UNIX sockets often have a mechanism to authenticate their peer processes. However, there is a requirement for care in order to avoid confused deputy attacks. Linux, for example, has two ways to pass ...
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How to read data from one userspace app to another userspace process

From userspace application I read some data using IOCtl from kernel driver synchronously. Now Iam planning to move the driver to userspace. Is there a way for my userspace app to read some data from ...
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Deleting the files from a SFTP server based modified time (SSH not enabled )

Need to delete the files from a sftp remote server based on last modified time .Files which are older then 30 days no need to keep in server .I have tried ls -lt ,but how to copy it to local machine ...
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How can a client talk to another client using unix domain sockets?

Using bash we might have something like this with netcat: nc -lk -U /my/fifo | while read line; do # line => {"client_id":123} done; clients send data like this: echo '{"client_id":123,"data":...
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1 vote
1 answer
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Sending data to Unix socket failing unless proxied with socat via UDP

I'm trying to debug why data isn't being sent over a Unix Domain Socket. I have 2 applications which should be communicating over a UDS but aren't. To test I've done the following: Using socat, I ...
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2 answers
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Unix Domain Socket bind, reuse address

If I bind() an AF_INET socket (for a TCP connection), then later close() it, next time I run my program, I may have issues, since despite the close(), the kernel can still have the resources ...
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Can one processes have a descriptor that is non-blocking while another process have a descriptor referencing the same file/socket that is blocking?

I am more interested in sockets than regular files, but basically I want to know whether one process can "see" a socket as blocking where another process can see it as non-blocking. I am guessing yes,...
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2 votes
2 answers
4k views

How many connections can there be between two Unix domain sockets?

From APUE: 17.3 Unique Connections A server can arrange for unique UNIX domain connections to clients using the standard bind, listen, and accept functions. Clients use connect to ...
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Must an application-layer protocol exist for communication between any two programs using sockets?

When any two programs, no matter how simple or complicated, communicate by internet domain sockets (or Unix domain sockets), does it necessarily imply that there is an application-layer protocol ...
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socat - UNIX-LISTEN and TCP-LISTEN in one command

Is it possible, to open a tcp port and a socket with one process/command? socat UNIX-LISTEN:/var/run/mysqld/mysqld.sock,fork,user=mysql,group=mysql,mode=777 TCP:123.123.123.1:3306 combined with: ...
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4 votes
1 answer
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Forward abstract unix socket over SSH?

I've discovered that OpenSSH is capable of forwarding UNIX sockets like this: ssh -R /var/run/program.sock:/var/run/program.sock My question is whether this extends to abstract unix sockets too. I'...
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Detect unix domain socket deletion?

Assume that you have an application that upon startup creates a unix domain socket and starts listening to it. Then any subsequent instance of the application connects to that socket, passes data to ...
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1 vote
1 answer
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It is possible to traceroute without touching ICMP?

I often run into a situation where I want to traceroute an IP without root or NET_RAW cap in Linux. I have attempted to send a UDP packet with a small TTL but no ttl error is emitted at all. It seems ...
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