<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div><br><br></div><div><br>On May 28, 2015, at 15:44, Jeff Frontz <<a href="mailto:jeff.frontz@gmail.com">jeff.frontz@gmail.com</a>> wrote:<br><br></div><blockquote type="cite"><div><div dir="ltr">I'm not quite sure what -z does (does it actually do a connect or just some subset of the TCP connection setup?), </div></div></blockquote><div><br></div><div><span style="background-color: rgba(255, 255, 255, 0);">Yep. -z is a TCP half-open. Sends SYN, waits for SYNACK and then quits. Makes it super easy (and scriptable) to test basic connectivity and catch firewall, service not running etc issues.</span></div><div><br></div><div>It is a much better version of what I often hear referred to as the "telnet test"</div><br><blockquote type="cite"><div><div dir="ltr">but is "traceroute -T -p 80 some host" roughly equivalent?</div></div></blockquote><div><br></div><div>Good thought but it does not appear so. That command is successful regardless of which port I try, including ones known not to be listening. It should fail with connection refused or at least exit non-zero. I'm not really sure what the port flag is doing - sending some kind of an ICMP echo message to that port?</div><div><br></div><br><blockquote type="cite"><div><div dir="ltr"><div><br></div></div></div></blockquote><div><br></div><div><br></div><br><blockquote type="cite"><div><div dir="ltr"><div><br></div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, May 28, 2015 at 3:53 PM, Rick Hornsby <span dir="ltr"><<a href="mailto:richardjhornsby@gmail.com" target="_blank">richardjhornsby@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br>
nc -zv somehost 80<br></blockquote></div></div></div>
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