"+ register cannot work in vim with clipboard support

Question

I guess my question may be similar to vim system register * and + not working but my server version is ubuntu. And I'm sure the installed vim has clipboard support. However, I cannot see the "+ register when I run :reg in vim. The followings are the commands I use to diagnose such condition but I still cannot find the solution.

First, I use ssh to connect to this server. To check the availability of clipboard support of Vim:

$ vim --version | grep clipboard
+clipboard       +insert_expand   +path_extra      +user_commands
+emacs_tags      +mouseshape      +startuptime     +xterm_clipboard

However, when I run :reg in one file opened by vim, I cannot see the system clipboard register. Here is what I got, (I removed the contents of these registers)

:reg
--- Registers ---
""
"0 
"1
"2
"3
"4 
"5 
"6
"7
"8
"9
"q 
"-
": 
"%   /usr/share/vim/vim74/doc/change.txt
"#   new.txt
"/   help registers

The os of this server is Ubuntu 16.04.4 LTS if this information can be helpful.

Also, I guess I have installed the dependencies of vim with clipboard, here is a subset of what I get when I run apt list --installed:

vim-common/xenial-updates,xenial-security,now 2:7.4.1689-3ubuntu1.2 amd64 [installed] vim-gnome/xenial-updates,xenial-security,now 2:7.4.1689-3ubuntu1.2 amd64 [installed] vim-gtk/xenial-updates,xenial-security,now 2:7.4.1689-3ubuntu1.2 amd64 [installed] vim-gui-common/xenial-updates,xenial-updates,xenial-security,xenial-security,now 2:7.4.1689-3ubuntu1.2 all [installed,automatic] vim-runtime/xenial-updates,xenial-updates,xenial-security,xenial-security,now 2:7.4.1689-3ubuntu1.2 all [installed,automatic] vim-tiny/xenial-updates,xenial-security,now 2:7.4.1689-3ubuntu1.2 amd64 [installed] vino/xenial-updates,now 3.8.1-0ubuntu9.2 amd64 [installed]

Answer 1

If you copy your text from your client, the text is being copied in the client-clipboard: "+@localhost.
So when using SSH, then starting Vim and type :reg, you can only see serverides registers, not client-side registers. "+@server is empty.