<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta content="text/html;charset=ISO-8859-15" http-equiv="Content-Type"> <title></title> </head> <body bgcolor="#ffffff" text="#000000"> Hi Peter, Peter Garrett schrieb: <blockquote cite="mid:20080405070529.26fe8dc8.peter.garrett@optusnet.com.au" type="cite"> <pre wrap="">On Fri, 04 Apr 2008 20:24:16 +0200 <a class="moz-txt-link-rfc2396E" href="mailto:ml@bortal.de">"ml@bortal.de"</a> <a class="moz-txt-link-rfc2396E" href="mailto:ml@bortal.de"><ml@bortal.de></a> wrote: </pre> <blockquote type="cite"> <pre wrap="">i would like to send some data from a netcat client to a netcat server. Can you set up the netcat server so that it echos what he recieves? </pre> </blockquote> <pre wrap=""> As I understand it, netcat acts as both a client and server, effectively, depending on which end you look at it from ;) So I'm not sure what you mean here. </pre> <blockquote type="cite"> <pre wrap="">Background: I would like to test my firewall setup if all my open ports (tcp and udp) work. So i want to send some data and check if the same data comes back. Can netcat do that? (no i dont want to use nmap :) ) </pre> </blockquote> <pre wrap=""> You can use netcat ( nc ) to "scan" ports - for example: </pre> </blockquote> I actually do not want to find open port, but test if my open ports can be reached (UDP and TCP). <blockquote cite="mid:20080405070529.26fe8dc8.peter.garrett@optusnet.com.au" type="cite"> <pre wrap=""> nc -w 2 -z name-or-IP 80 checks if the system at "name-or-IP" is listening on port 80 . The -w option is a "timeout" in seconds. If successful, nc exits silently. If not, you see an error message. For example: $ nc -w 2 -z archive.ubuntu.com 80 # OK - silent exit $ nc -w 2 -z archive.ubuntu.com.bogus 80 archive.ubuntu.com.bogus: forward host lookup failed: Unknown host : Connection timed out </pre> </blockquote> A UDP Port never replies by default. Thats why i need some client/server setup to check if the udp port is really open (or better: if the udp port is allowed by the firewall inbetween!) Thanks, Mario <blockquote cite="mid:20080405070529.26fe8dc8.peter.garrett@optusnet.com.au" type="cite"> <pre wrap=""> Peter </pre> </blockquote> </body> </html>