The VideoLAN Forums

I am using VLC to access an RTSP stream over the network. When I connect from a client via a firewall that has all ports open from client -> server I experience a startup delay of 12 sec. If I try the same from a client on the same subnet then the delay is only 1sec.

Monitoring the firewall I can see VLC is accessing 5 times on UDP port 4893 and getting a "Close - ICMP Unreach" log entries.

What is vlc trying to do on this port and would this cause delays through networks + firewalls?

The ping and trace routes are reporting <1ms response times, and only 1 hop. The network guys say its something at the application level.

Because RTSP transmits data over UDP by default.

thanks for the reply, but why udp from vlc to server cause cause a delay through an open firewall/network rather than on a local subnet?

Because network address translation and/or firewalling is blocking the UDP stream.