$ ffmpeg -listen -i rtmp://localhost/live/test -c copy output.mp4
ffmpeg version 2.4.3 Copyright (c) 2000-2014 the FFmpeg developers
  built on Oct 19 2015 11:19:11 with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04)
  configuration: --prefix=/tmp/ffmpeg-build --extra-cflags=-I/tmp/ffmpeg-build/include --extra-ldflags=-L/tmp/ffmpeg-build/lib --bindir=/tmp/ffmpeg-build/bin --enable-gpl --enable-libass --enable-libfdk-aac --enable-libfreetype --enable-libmp3lame --enable-libtheora --enable-libvorbis --enable-libx264 --enable-nonfree
  libavutil      54.  7.100 / 54.  7.100
  libavcodec     56.  1.100 / 56.  1.100
  libavformat    56.  4.101 / 56.  4.101
  libavdevice    56.  0.100 / 56.  0.100
  libavfilter     5.  1.100 /  5.  1.100
  libswscale      3.  0.100 /  3.  0.100
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  0.100 / 53.  0.100
[NULL @ 0x1bcfe20] Unable to find a suitable output format for 'rtmp://localhost/live/test'
rtmp://localhost/live/test: Invalid argument