Technical Memo: LPD COMPATIBILITY





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LPD COMPATIBILITY

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Using ScriptServer® for OpenVMS lpd Compatibility

When starting a ScriptServer queue on a networked printer with the lpd protocol, the "device" on which to start a queue must be designated in the following format:

  $ START/QUE/ON="remote_queue@tcpip_address"/PROC=SSV$SMB/LIB=SSV$DEVCTL/DEFAULT=FEED

NOTE: The device (remote queue) specification is case sensitive. If you are using ScriptServer's "gethostbyname" support, the printer node name can be substituted for the tcpip_address.

The remote queue name varies with each network printer card manufacturer. There are usually at least two "queues" on every card, one for text files that inserts line feeds after each line, and one for PostScript that will not alter the data. ScriptServer requires that you select the PostScript or "raw" remote queue.

The following examples use a TCP/IP printer with an address of "192.100.10.2" on each of the network cards that are compatible with ScriptServer lpd support. This information can also be entered in the SSV$CONFIG queue creation procedure.

Card/Printer Remote Queue Example
XCD XJetIV HP_PRINTER $ START/QUE/ON="HP_PRINTER@192.100.10.2" queue
HP JetDirect raw $ START/QUE/ON="raw@192.100.10.2" queue
QMS/Crown* lp $ START/QUE/ON="lp@192.100.10.2" queue
Dataproducts lpd** $ START/QUE/ON="lpd_queue@192.100.10.2" queue
Emulex NETJet PASSTHRU $ START/QUE/ON="PASSTHRU@192.100.10.2" queue
Axis Print Server 560 PR1,PR2, or PR3 $ START/QUE/ON="PR1@192.100.10.2" queue
Cannon xjprint $ START/QUE/ON="xjprint@192.100.10.2" queue

NOTES:
* For lpd protocol to work properly on QMS/Crown printers, SPOOLING must beturned ON in the TCP/IP - DECNET sub-menu. This will prevent jobs from being lost on the printer.
** lpd is a "lpd gateway" on the DataProducts VPT printers that must be configured to point to a lpd server queue, in this example, "lpd_queue".

TCP/IP Compatibility Issues

One of the TCP/IP protocol options is packet coalescence, where the send operation will be delayed to fill up the send buffer for more efficient I/O operations. Whether or not packets are coalesced is determined by the combination of the TCP/IP stack being used and the TCP/IP card on the printer. In some cases, packet coalescence can break the lpd protocol. To prevent this, ScriptServer does not coalesce packets by default, but allows the use of a logical to explicitly enable packet coalescence as follows:

  $ DEFINE/SYSTEM SSV$queue_name_LPD_COALESCE  TRUE

ScriptServer also may be connected to a printer or another system that is unable to send the appropriate acknowledgment packets. This will disable the ScriptServer queue. If you wish to attempt to run the queue without these "ACK" packets, disable ScriptServer from attempting to read them with the logical:

  $ DEFINE/SYSTEM SSV$device_LPD_READ FALSE

Card/Printer	Remote Queue	Example
XCD XJetIV	`HP_PRINTER`	`$ START/QUE/ON="HP_PRINTER@192.100.10.2"` queue
HP JetDirect	`raw`	`$ START/QUE/ON="raw@192.100.10.2"` queue
QMS/Crown*	`lp`	`$ START/QUE/ON="lp@192.100.10.2"` queue
Dataproducts	`lpd`**	`$ START/QUE/ON="lpd_queue@192.100.10.2"` queue
Emulex NETJet	`PASSTHRU`	`$ START/QUE/ON="PASSTHRU@192.100.10.2"` queue
Axis Print Server 560	`PR1,PR2`, or `PR3`	`$ START/QUE/ON="PR1@192.100.10.2"` queue
Cannon	`xjprint`	`$ START/QUE/ON="xjprint@192.100.10.2"` queue

NOTES:
*	For lpd protocol to work properly on QMS/Crown printers, SPOOLING must beturned ON in the TCP/IP - DECNET sub-menu. This will prevent jobs from being lost on the printer.
**	lpd is a "lpd gateway" on the DataProducts VPT printers that must be configured to point to a lpd server queue, in this example, "lpd_queue".