One simple improvement that solves my previous ssh copy pain on remote vim...

Just Three Functions

In your Vim config:

function! GetVisualSelection()
  try
    let a_save = @a
    normal! gv"ay
    return @a
  finally
    let @a = a_save
  endtry
endfunction

function CopyToNetCat() range
    let selected_lines = GetVisualSelection()
    echo system('printf "%s" '.shellescape(selected_lines).' | nc localhost 2000')
endfunction

and probably bind it like this:

vnoremap <C-y> :call CopyToNetCat()<CR>

In your Mac shell script (Linux should replace pbcopy with xclip -sel clip or xsel -i -b ):

ssh_copy() {
    while ! (nc -l 2000 | pbcopy) || true; do ; done &
    copy_daemon=$!
    ssh $@ -R 2000:localhost:2000
    pkill -9 -g $copy_daemon
}

Now, you login with ssh_copy user@server instead of normal ssh to remote and have fun there with Ctrl+y. Also feel free to change the port number if 2000 is too familar to you.

If Multiple SSH Sessions Bother You

Just forcefully kick out your dups session:

ssh_copy() {
    echo "Make sure you setup password free by doing: ssh-copy-id id@server"
    # clean all other ssh session
    ssh ${1} -t 'ps -aux | grep "[s]sh" | grep pts/ | grep -v $(ps --no-headers -fp $$ | awk "{print \$3}") | awk "{print \$2}" | xargs kill -9'
    while ! (nc -l 2000 | pbcopy) || true; do ; done &
    copy_daemon=$!
    ssh ${1} -R 2000:localhost:2000 -t 'tmux a || $SHELL '
    pkill -9 -g $copy_daemon
}

Bonus: No +clipboard or DISPLAY

Symptoms: SSHed in the same remote server, with no +clipboard or $DISPLAY, thus unamedplus, xsel or xclip would not work in different tmux session etc.

Treatment: ancient/traditional copy via tmp files. Map keys to these functions.

function CopyToTmpBuffer() range
    let selected_lines = GetVisualSelection()
    echo system('printf "%s" '.shellescape(selected_lines).' > ~/.config/nvim/backup/.vim-buf')
endfunction
function PasteFromTmpBuffer()
    try
        let a_save = @a
        let @a = system('cat ~/.config/nvim/backup/.vim-buf')
        normal! "ap
    finally
        let @a = a_save
    endtry
endfunction