weiwei wrote: look under window XP for it driver, it creates a port which points to routers IP address and then LPT1 for printing.
That's a virtual "LPT1:" port, not a real one.
weiwei wrote: I tried to mimic the setup in Linux Mint
Linux is not Windows
weiwei wrote: 1. I selected network printer, then TCP/SOCKET, HP jDirect, RawConnection
2. I typed in my router's IP address
3. on Port, system assign port 9100 by itself.
weiwei wrote: I have tried many different setting on port, but none of them work. I tried LPT 1, LPT #1, lpt1, LPT1.
Linux is not Windows. Linux is not MS-DOS. Using MS-DOS device names in Linux is not very likely to work. Besides: "port" here means TCP/IP port. 9100 tcp is the standard target port for UNIX-style network printing.
weiwei wrote: But when I connect directly to the printer via Parallel cable, it prints fine. so the driver is not the issue here.
No, it's clearly your networking setup. Why not use the printer directly on the Linux computer? You can use Linux to share the printer on the rest of the network ... it's a server operating system after all