add proc node /proc/net/udp to show the active udp connections from procfs nuttx style: server> cat /proc/net/udp UDP sl local_address remote_address flg txsz rxsz (IPv4) 1: 0.0.0.0: 5285 192.168.31.22: 7779 9 0 1041 2: 0.0.0.0: 5286 192.168.31.22: 7779 9 0 1041 3: 0.0.0.0: 5287 192.168.31.22: 7779 9 0 1041 linux kernel: https://www.kernel.org/doc/Documentation/networking/proc_net_tcp.txt Signed-off-by: chao an <anchao@xiaomi.com>