printer problem

[Vu Pham]

I have a network printer using LPD. When I *manually* telnet to that 
printer at LPD port, then the printer does ACK to my SYN packet and 
start receiving data.

When I use CUPS to print, then the printer does not acknowledge the tcp 
SYN packets at all.

They are just TCP connections, how does the printer know ? :(
Below is my tcpdump:
All packets before 14:24:54 are from my manual telnet.
All packets after 14:25:06 are from CUPS.
Pluto is my server, 192.168.1.110 is the printer

As you can see, CUPS attempted to send SYN packets but does not get ACKED.

I can only see the difference of the source ports, but does the printer 
care about that ?

-------------- start of tcpdump -------
[root at jetco ~]# tcpdump host 192.168.1.110
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes
14:24:50.555796 IP pluto.51602 > 192.168.1.110.printer: S 
3462708113:3462708113(0) win 5840 <mss 1460,nop,nop,sackOK,nop,wscale 2>
14:24:50.764192 IP 192.168.1.110.printer > pluto.51602: S 
3520144456:3520144456(0) ack 3462708114 win 4096 <mss 1452,nop,wscale 0>
14:24:50.764207 IP pluto.51602 > 192.168.1.110.printer: . ack 1 win 1460
14:24:54.396898 IP pluto.51602 > 192.168.1.110.printer: F 1:1(0) ack 1 
win 1460
14:24:54.409157 IP 192.168.1.110.printer > pluto.51602: . ack 2 win 4380
14:24:54.409700 IP 192.168.1.110.printer > pluto.51602: F 1:1(0) ack 2 
win 4380
14:24:54.409714 IP pluto.51602 > 192.168.1.110.printer: . ack 2 win 1460



14:25:06.560950 IP pluto.731 > 192.168.1.110.printer: S 
3473251429:3473251429(0) win 5840 <mss 1460,nop,nop,sackOK,nop,wscale 2>
14:25:09.560695 IP pluto.731 > 192.168.1.110.printer: S 
3473251429:3473251429(0) win 5840 <mss 1460,nop,nop,sackOK,nop,wscale 2>
14:25:15.560267 IP pluto.731 > 192.168.1.110.printer: S 
3473251429:3473251429(0) win 5840 <mss 1460,nop,nop,sackOK,nop,wscale 2>
-------------- end of tcpdump -------

Any advice, please  ?

Thanks,

Vu