title: Mac: SSH doesn't work anymore without changing something
body: <p>After searching the web for one day without a good solution I'm here to tell you my problem.</p>
  
  <p>Three days ago I set up a SSH-key to use git with SSH. Everything worked fine and I was able to push and pull everything to GitHub. Since yesterday I'm not able to do it anymore. I always get the same error (shown below). SSH-key is part of the ssh-agent, config-files weren't changed and even a normal connection through SSH to GitHub is not possible. Tried it with other projects and other repos as well and got the same error. I didn't update Sierra or something else in the last days, so this can't be the reason as well.</p>
  
  <p>Terminal in- and output:</p>
  
  <pre><code>User-MBP:data-analysis user$ git push -v origin master
  Pushing to git@github.com:Username/data-analysis.git
  ssh_exchange_identification: Connection closed by remote host
  fatal: Could not read from remote repository.
  
  Please make sure you have the correct access rights
  and the repository exists.
  </code></pre>
  
  <p>Normal SSH-connection:</p>
  
  <pre><code>User-MBP:data-analysis user$ ssh -v git@github.com
  OpenSSH_7.4p1, LibreSSL 2.5.0
  debug1: Reading configuration data /Users/user/.ssh/config
  debug1: /Users/user/.ssh/config line 1: Applying options for *
  debug1: Reading configuration data /etc/ssh/ssh_config
  debug1: Connecting to github.com [192.30.253.113] port 443.
  debug1: Connection established.
  debug1: identity file /Users/user/.ssh/id_rsa type 1
  debug1: key_load_public: No such file or directory
  debug1: identity file /Users/user/.ssh/id_rsa-cert type -1
  debug1: Enabling compatibility mode for protocol 2.0
  debug1: Local version string SSH-2.0-OpenSSH_7.4
  ssh_exchange_identification: Connection closed by remote host
  </code></pre>
  
  <p>Thank you for your help!</p>
  
  <p><strong>UPDATE</strong></p>
  
  <p>Changed port back to 22 to get the following:</p>
  
  <pre><code>User-MBP:data-analysis user$ git push origin master
  ssh: connect to host github.com port 22: Connection refused
  fatal: Could not read from remote repository.
  
  Please make sure you have the correct access rights
  and the repository exists.
  </code></pre>
  
  <p>and</p>
  
  <pre><code>User-MBP:data-analysis user$ ssh -v git@github.com
  OpenSSH_7.4p1, LibreSSL 2.5.0
  debug1: Reading configuration data /Users/user/.ssh/config
  debug1: /Users/user/.ssh/config line 1: Applying options for *
  debug1: Reading configuration data /etc/ssh/ssh_config
  debug1: Connecting to github.com [192.30.253.113] port 22.
  debug1: connect to address 192.30.253.113 port 22: Connection refused
  debug1: Connecting to github.com [192.30.253.112] port 22.
  debug1: connect to address 192.30.253.112 port 22: Connection refused
  ssh: connect to host github.com port 22: Connection refused
  </code></pre>