• redirect outgoing RTMP traffic to localhost:

iptables -t nat -A OUTPUT -p tcp --dport 1935 -j REDIRECT

• run rtmpsrv:

rtmpsrv

• browse the page containing media streamed over RTMP
• rtmpsrv will output an rtmpdump command that can be used to download videos
• stop rtmpsrv with CTRL-C
• remove the RTMP traffic redirection:

iptables -t nat -D OUTPUT -p tcp --dport 1935 -j REDIRECT

• run the rtpmdump command from the rtmpsrv output to download the video