"lp: unable to print file: server-error-service-unavailable"

[manfred.schaumburg at arcor.de]

I installed cups on a server and printing via lp works fine.
But if i try to access the server from an other client via lp i get
the message "lp: unable to print file: server-error-service-unavailable".
I configured the Servername in /etc/cups/client.conf. On the client
lpstat -t shows
scheduler is running
no system default destination
lpstat: get-classes failed: server-error-service-unavailable
lpstat: get-printers failed: server-error-service-unavailable
lpstat: get-printers failed: server-error-service-unavailable
lpstat: get-printers failed: server-error-service-unavailable
lpstat: get-jobs failed: server-error-service-unavailable
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Why is it not possible to access the server from a client on an other computer?