title: Why am I getting a "failed to connect to server" message from tmux when I try to list sessions?
body: <p>Here's what's happening to me: I start tmux sessions using <code>tmux -L name1</code>, <code>tmux -L name2</code>; then I detatch them using <kbd>ctrl</kbd>+<kbd>B</kbd>+<kbd>d</kbd>. Then I try to get a list of the currently running sessions on my computer. However, when I run <code>tmux ls</code>, I get an error message: </p>
  
  <pre><code>failed to connect to server: Connection refused
  </code></pre>
  
  <p>Is this a bug? I'm familiar with screen; I regard <code>screen -ls</code> as a very useful function since I might start a session and leave it running for weeks before the next time I attach to it. Because of this, the ability to list current running tmux sessions is quite important for me. Why does <code>tmux ls</code> return a "connection refused" error when I know tmux is running?</p>