netcatで送信を行うとき、うまくコマンドが閉じないケースがあります。
とくにUDPだとそのまんまです。
このとき、-cオプションを使うとうまく閉じる事ができます。
実際のところ
パイプに繋げたUDP通信で、送ったきり閉じてしまいたい時は以下のようにします。
$ echo -n '1 2 3' | netcat -u -c URL PORT
なぜかmanにない!?
……どういうわけか、このオプションはmanだと出てきません……
ところが-hだと出てきます。
なんでじゃ……？？
$ nc -h GNU netcat 0.7.1, a rewrite of the famous networking tool. Basic usages: connect to somewhere: nc [options] hostname port [port] ... listen for inbound: nc -l -p port [options] [hostname] [port] ... tunnel to somewhere: nc -L hostname:port -p port [options] Mandatory arguments to long options are mandatory for short options too. Options: -c, --close close connection on EOF from stdin -e, --exec=PROGRAM program to exec after connect -g, --gateway=LIST source-routing hop point[s], up to 8 -G, --pointer=NUM source-routing pointer: 4, 8, 12, ... -h, --help display this help and exit -i, --interval=SECS delay interval for lines sent, ports scanned -l, --listen listen mode, for inbound connects -L, --tunnel=ADDRESS:PORT forward local port to remote address -n, --dont-resolve numeric-only IP addresses, no DNS -o, --output=FILE output hexdump traffic to FILE (implies -x) -p, --local-port=NUM local port number -r, --randomize randomize local and remote ports -s, --source=ADDRESS local source address (ip or hostname) -t, --tcp TCP mode (default) -T, --telnet answer using TELNET negotiation -u, --udp UDP mode -v, --verbose verbose (use twice to be more verbose) -V, --version output version information and exit -x, --hexdump hexdump incoming and outgoing traffic -w, --wait=SECS timeout for connects and final net reads -z, --zero zero-I/O mode (used for scanning) Remote port number can also be specified as range. Example: '1-1024'
