首先安装（Ubuntu系统）
apt update apt-get install netcat
命令格式 具体用法
nc -h
OpenBSD netcat (Debian patchlevel 1.218-4ubuntu1)
usage: nc [-46CDdFhklNnrStUuvZz] [-I length] [-i interval] [-M ttl]
[-m minttl] [-O length] [-P proxy_username] [-p source_port]
[-q seconds] [-s sourceaddr] [-T keyword] [-V rtable] [-W recvlimit]
[-w timeout] [-X proxy_protocol] [-x proxy_address[:port]]
[destination] [port]
Command Summary:
-4 Use IPv4
-6 Use IPv6
-b Allow broadcast
-C Send CRLF as line-ending
-D Enable the debug socket option
-d Detach from stdin
-F Pass socket fd
-h This help text
-I length TCP receive buffer length
-i interval Delay interval for lines sent, ports scanned
-k Keep inbound sockets open for multiple connects
-l Listen mode, for inbound connects
-M ttl Outgoing TTL / Hop Limit
-m minttl Minimum incoming TTL / Hop Limit
-N Shutdown the network socket after EOF on stdin
-n Suppress name/port resolutions
-O length TCP send buffer length
-P proxyuser Username for proxy authentication
-p port Specify local port for remote connects
-q secs quit after EOF on stdin and delay of secs
-r Randomize remote ports
-S Enable the TCP MD5 signature option
-s sourceaddr Local source address
-T keyword TOS value
-t Answer TELNET negotiation
-U Use UNIX domain socket
-u UDP mode
-V rtable Specify alternate routing table
-v Verbose
-W recvlimit Terminate after receiving a number of packets
-w timeout Timeout for connects and final net reads
-X proto Proxy protocol: "4", "5" (SOCKS) or "connect"
-x addr[:port] Specify proxy address and port
-Z DCCP mode
-z Zero-I/O mode [used for scanning]
常用，测试UDP端口是否开通
nc -vzu 172.18.1.1 161
标签：socket,connects,命令,length,proxy,使用,netcat,port,mode From： https://www.cnblogs.com/chuhe42/p/17734168.html