lsof: What the numbers inside socket parentheses represent
When I run the lsof command, in the name column, for sockets, some numbers appear in parentheses as shown below. What do you mean?
command pid user fd Name process 8197 root 29 socket:
TL;DR: A unique number associated with the socket
One of the defining rules of Unix is “Everything is a file”. Because sockets are also represented by very special file systems, often referred to as sockfs.
Files on traditional file systems have inode-numbers — unique numbers that allow them to be identified:
$ ls -li /bin/bash 7864369 -rwxr-xr-x 1 root root 656584 Oct 15 2014 /bin/bash ^^^^^^^ inode-number
The same applies to Sockfs, all sockets also have inode-numbers.
For special file systems that do not have an actual file naming pattern, all files have a common name of the form
fsname:[inode-number] (see also: linux+v3.19.1/fs/dcache.c#L2945)