knockd

Using knockd to do stuff | Sending TCP/UPD Requests via PHP

I was wondering, whether knockd http://www.zeroflux.org/cgi-bin/cvstrac.cgi/knock/wiki would be a good was to be able to restart apache without logging into ssh. But my programming question was whether there is a way to send tcp/udp packages via PHP so I can knock via a webclient. I am aware that this is not the safest way of doing it, ...

ssh/VPN access from dynamic IPs / while travelling. knockd or dynDNS based authentication?

What are the advantages and disadvantages of using knockd vs. using dynamic DNS based authentication for ssh or VPN logins from a dynamic IP address or while travelling (i.e. some random hotel IP)? Ideally, any device with ssh/VPN client capability should be able to use whatever additional client software is necessary. (The alternative...