TechTalk: TCP/IP

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From: Ron Hodgson

To: All

I have a question about using TCP/IP to connect PCs to an AS/400 rather than PC Support's APPC.

MC had some very compelling arguments in favor of using TCP/IP (see "Using TCP/IP with Windows," MC, August 1995). One possible drawback not discussed goes to the heart of my question.

Isn't it true that TCP/IP does not provide the AS/400 printer emulation support that we've all become so dependent upon? If so, how do you provide the needed capabilities?

From: Fred Gamache

To: Ron Hodgson

We are using TCP/IP and, while we don't use printer emulation, we do have an AS/400 queue set up to automatically send any spool files on it to a network print queue. So, we are using our network-connected printers to print. We use the LPD function in TCP/IP to do this.

From: Ron Hodgson

To: Fred Gamache

Can you explain what LPD is? It's interesting that you mentioned this form of printer redirection. We're looking at implementing an optical archiving system, and I'd like it to be LAN-based yet still pull print files from the AS/400. Routing selected system output to NetWare queues is one consideration.

From: Fred Gamache

To: Ron Hodgson

The following information from AS/400 TCP/IP Configuration and Reference V3R1 (SC41-3420, CD-ROM QBKANL) describes the LPD function. As I said, we are sending print files to a variety of network-attached printers and it seems to be working OK.

You can request to have your spooled files sent, received, and printed on any system in your TCP/IP network. The term often used by UNIX TCP/IP software to describe this support is line printer requester (LPR). LPR is the sending, or client portion, of a spooled file transfer. On the AS/400 system, the Send TCP/IP Spooled File (SND-TCPSPLF) command provides this function by allowing you to specify what system you want the spooled file printed on and how you want it printed. There is also a TCP/IP command, LPR, that provides the same parameters and function as the SNDTCPSPLF command.

The printing of the file is done by the printing facilities of the destination system. The destination system must be running TCP/IP. On the AS/400 system, the line printer daemon (LPD) is the process on the destination system that receives the file sent by the SNDTCPSPLF command. The LPD process places the spooled file on a local printer queue. To print the spooled file, the spooled file must be put on a printer queue already started to an active printer writer or a writer must be started to that printer queue.

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