Where is wrong with tcpdump?

[EdwardKing]

I want to watch ip:172.0.10.2 port:19 TCP information,so I use following command:
#tcpdump tcp port 19 host 172.0.10.2
tcpdump: syntax error

Why? How to do it?

Thanks


----------------------------------------------------------------------------------------------
Confidentiality Notice: The information contained in this e-mail and any
accompanying attachment(s) is intended only for the use of the intended
recipient and may be confidential and/or privileged of Neusoft Corporation, its subsidiaries and/or its affiliates. If any reader of this communication is not the intended recipient, unauthorized use, forwarding, printing, storing, disclosure or copying is strictly prohibited, and may be unlawful. If you have received this communication in error, please immediately notify the sender by return e-mail, and delete the original message and all copies from your system. Thank you. 
-----------------------------------------------------------------------------------------------