nc(netcat)被譽為網絡工具中的“瑞士軍刀”，體積雖小但功能強大，nc最簡單的功能是端口掃描，這里我主要筆記一下它作為文件傳輸的妙用。
首先看一下幫助信息。
$ nc -h
OpenBSD netcat (Debian patchlevel 1.105-7ubuntu1)
This is nc from the netcat-openbsd package. An alternative nc is available
in the netcat-traditional package.
usage: nc [-46bCDdhjklnrStUuvZz] [-I length] [-i interval] [-O length]
[-P proxy_username] [-p source_port] [-q seconds] [-s source]
[-T toskeyword] [-V rtable] [-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
-h This help text
-I length TCP receive buffer length
-i secs Delay interval for lines sent, ports scanned
-j Use jumbo frame
-k Keep inbound sockets open for multiple connects
-l Listen mode, for inbound connects
-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 addr Local source address
-T toskeyword Set IP Type of Service
-t Answer TELNET negotiation
-U Use UNIX domain socket
-u UDP mode
-V rtable Specify alternate routing table
-v Verbose
-w secs 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]
Port numbers can be individual or ranges: lo-hi [inclusive]
端口掃描：
$ nc -z -v -n 127.0.0.1 20-100
...
Connection to 127.0.0.1 80 port [tcp/*] succeeded!
...
簡單文件傳輸：
客戶端：
$ nc -l 192.168.1.11 1234 > passwd.txt
服務端：
$ nc 192.168.1.11 1234 /etc/passwd
也可以是
cat /etc/passwd | nc 192.168.1.11 1234
服務端ip是192.169.1.11，端口是1234
如此，當兩臺linux機器需要簡單傳輸文件時，再好不過了～
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- Linux利用nc命令監控服務器端口的方法
