Arif, You would want to run tcpdump (or some other sniffer() on the host server, so that you can confirm that there is two-way traffic. If tcpdump on the host server does not show any traffic from your client, something is blocking inbound. If you see traffic coming into the server, but nothing returning, you probably have issues around OSI layers 5-7. If you see a response, but you did not see from your client, then it may something blocking return traffic. - Rilindo -----Original Message----- From: centos-bounces at centos.org [mailto:centos-bounces at centos.org] On Behalf Of Arif Hossain Sent: Wednesday, March 14, 2012 8:25 AM To: centos at centos.org Subject: [CentOS] testing a udp socket with netcat i've this udp daemon which is waiting for an incoming udp datagram. now i want test this daemon for random garbage to test how it behaves. My udp daemon is running because its shows on netstat. problem is if i issue following command for putting udp datagram : $nc -uvvz <host> <port> it does not output any thing. i have straced the udp daemon. which does not returns from recv() call. my goal is to put arbitrary data on the udp socket by netcat. i do not have any experience regarding netcat so i'm asking if anyone can help me out with this. thanks in advance. -- "You have a voice" ----The King's Speech Public Key : $ gpg --keyserver keyserver.ubuntu.com --recv-key C88CFC23 This message, including any attachments, is the property of Sears Holdings Corporation and/or one of its subsidiaries. It is confidential and may contain proprietary or legally privileged information. If you are not the intended recipient, please delete it without reading the contents. Thank you.