linux nc命令

时间：2014-05-26 07:56:47 收藏：0 阅读：607

即NetCat简写，在网络工具中有“瑞士军刀”美誉，其有Windows和Linux的版本。因为它短小精悍（1.84版本也不过25k，旧版本或缩减版甚至更小）、功能实用，被设计为一个简单、可靠的网络工具，可通过TCP或UDP协议传输读写数据。同时，它还是一个网络应用Debug分析器，因为它可以根据需要创建各种不同类型的网络连接。NetCat 官方地址：http://netcat.sourceforge.net/

功能说明：功能强大的网络工具
语　　法：nc [-hlnruz][-g<网关...>][-G<指向器数目>][-i<延迟秒数>][-o<输出文件>][-p<通信端口>][-s<来源位址>][-v...][-w<超时秒数>][主机名称][通信端口...]
参　　数：
  -g   <网关>   设置路由器跃程通信网关，最多可设置8个。
  -G   <指向器数目>   设置来源路由指向器，其数值为4的倍数。
  -h   在线帮助。
  -i   <延迟秒数>   设置时间间隔，以便传送信息及扫描通信端口。
  -l   使用监听模式，管控传入的资料。
  -n   直接使用IP地址，而不通过域名服务器。
  -o   <输出文件>   指定文件名称，把往来传输的数据以16进制字码倾倒成该文件保存。
  -p   <通信端口>   设置本地主机使用的通信端口。
  -r   乱数指定本地与远端主机的通信端口。
  -s   <来源位址>   设置本地主机送出数据包的IP地址。
  -u   使用UDP传输协议。
  -v   显示指令执行过程。
  -w   <超时秒数>   设置等待连线的时间。
  -z   使用0输入/输出模式，只在扫描通信端口时使用。

1.端口扫描

[root@rusky2 ~]# nc -v  192.168.2.100 -z 11162-11170
Connection to 192.168.2.100 11162 port [tcp/suncacao-jmxmp] succeeded!
Connection to 192.168.2.100 11163 port [tcp/suncacao-rmi] succeeded!
Connection to 192.168.2.100 11164 port [tcp/suncacao-csa] succeeded!
nc: connect to 192.168.2.100 port 11165 (tcp) failed: Connection refused
nc: connect to 192.168.2.100 port 11166 (tcp) failed: Connection refused
nc: connect to 192.168.2.100 port 11167 (tcp) failed: Connection refused
nc: connect to 192.168.2.100 port 11168 (tcp) failed: Connection refused
nc: connect to 192.168.2.100 port 11169 (tcp) failed: Connection refused
nc: connect to 192.168.2.100 port 11170 (tcp) failed: Connection refused

不加-v参数，则只显示已打开的端口

[root@rusky2 ~]# nc   192.168.2.100 -z 11162-11170
Connection to 192.168.2.100 11162 port [tcp/suncacao-jmxmp] succeeded!
Connection to 192.168.2.100 11163 port [tcp/suncacao-rmi] succeeded!
Connection to 192.168.2.100 11164 port [tcp/suncacao-csa] succeeded!

2、简单聊天工具

[root@rusky ~]# nc -l 1234   #rusky开始端口1234
hello rusky
hello rusky2
[root@rusky2 ~]# nc 192.168.2.100 1234 　　#rusk2连接端口1234
hello rusky
hello rusky2

[root@rusky ~]# netstat -an | grep 1234
tcp 0 0 0.0.0.0:1234 0.0.0.0:* LISTEN
tcp 0 0 192.168.2.100:1234 192.168.2.200:58039 ESTABLISHED

3.。。。。。。。。　　　　　　

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[root@YncmIAM-ESP-a ~]# man 1 nc
NC(1)                     BSD General Commands Manual                    NC(1)
 
NAME
     nc - arbitrary TCP and UDP connections and listens
 
SYNOPSIS
     nc [-46DdhklnrStUuvz] [-i interval] [-p source_port] [-s source_ip_address] [-T ToS] [-w timeout]
        [-X proxy_protocol] [-x proxy_address[:port]] [hostname] [port[s]]
 
DESCRIPTION
     The nc (or netcat) utility is 
used for 
just about anything under the sun involving TCP or UDP.  It can
     open TCP connections, send UDP packets, listen on 
arbitrary TCP and UDP ports, do 
port scanning, and
     deal with both IPv4 and IPv6.  Unlike telnet(1), nc scripts nicely, and separates error messages onto
     standard error instead of sending them to standard output, as 
telnet(1) does with some.
 
     Common uses include:
 
           ??¤   simple TCP proxies
           ??¤   shell-script based HTTP clients and servers
           ??¤   network daemon testing
           ??¤   a SOCKS or HTTP ProxyCommand for 
ssh(1)
           ??¤   and much, much more
 
     The options are as 
follows:
 
     -4      Forces nc to use IPv4 addresses only.
 
     -6      Forces nc to use IPv6 addresses only.
 
     -D      Enable debugging on 
the socket.
 
     -d      Do not attempt to read from 
stdin.
 
     -h      Prints out 
nc help.
 
     -i interval
             Specifies a delay time interval between lines of text sent and received.  Also causes a delay
             time between connections to multiple ports.
 
     -k      Forces nc to stay listening for 
another connection after its current connection is 
completed.
             It is 
an error to use this 
option without the -l option.
 
     -l      Used to specify that nc should listen for 
an incoming connection rather than initiate a con-
             nection to a remote host.  It is 
an error to use this 
option in 
conjunction with the -p, -s,
             or -z options.  Additionally, any timeouts specified with the -w option are ignored.
 
     -n      Do not do 
any DNS or service lookups on 
any specified addresses, hostnames or ports.
 
     -p source_port
             Specifies the source port nc should use, subject to privilege restrictions and availability.
             It is 
an error to use this 
option in 
conjunction with the -l option.
 
     -r      Specifies that source and/or destination ports should be chosen randomly instead of sequen-
             tially within a range or in 
the order that the system assigns them.
 
     -S      Enables the RFC 2385 TCP MD5 signature option.
 
     -s source_ip_address
             Specifies the IP of the interface 
which is 
used to send the packets.  It is 
an error to use
             this 
option in 
conjunction with the -l option.
 
     -T ToS  Specifies IP Type of Service (ToS) for 
the connection.  Valid values are the tokens
             ?°lowdelay?±, ?°throughput?±, ?°reliability?±, or an 8-bit hexadecimal value preceded by 
?°0x?±.
 
     -t      Causes nc to send RFC 854 DON?ˉT and WON?ˉT responses to RFC 854 DO and WILL requests.  This
             makes it possible to use nc to script telnet sessions.
 
     -U      Specifies to use Unix Domain Sockets.
 
     -u      Use UDP instead of the default 
option of TCP.
 
     -v      Have nc give more verbose output.
 
     -w timeout
             If a connection and stdin are idle for 
more than timeout seconds, then the connection is
             silently closed.  The -w flag has no effect on 
the -l option, i.e. nc will listen forever for
             a connection, with or without the -w flag.  The default 
is no timeout.
 
     -X proxy_version
             Requests that nc should use the specified protocol when talking to the proxy server.  Sup-
             ported protocols are ?°4?± (SOCKS v.4), ?°5?± (SOCKS v.5) and ?°connect?± (HTTPS proxy).  If the
             protocol is 
not specified, SOCKS version 5 is 
used.
 
     -x proxy_address[:port]
             Requests that nc should connect to hostname using 
a proxy at proxy_address and port.  If port
             is 
not specified, the well-known port for 
the proxy protocol is 
used (1080 for 
SOCKS, 3128 for
             HTTPS).
 
     -z      Specifies that nc should just scan for 
listening daemons, without sending any data to them.
             It is 
an error to use this 
option in 
conjunction with the -l option.
 
     hostname can be a numerical IP address or a symbolic hostname (unless the -n option is 
given).  In
     general, a hostname must be specified, unless the -l option is 
given (in 
which case 
the local host is
     used).
 
     port[s] can be single integers or ranges.  Ranges are in 
the form nn-mm.  In general, a destination
     port must be specified, unless the -U option is 
given (in 
which case 
a socket must be specified).
 
CLIENT/SERVER MODEL
     It is 
quite simple to build a very basic client/server model using 
nc.  On one console, start nc lis-
     tening on 
a specific port for 
a connection.  For example:
 
           $ nc -l 1234
 
     nc is 
now listening on 
port 1234 for 
a connection.  On a second console (or a second machine), connect
     to the machine and port being listened on:
 
           $ nc 127.0.0.1 1234
 
     There should now be a connection between the ports.  Anything typed at the second console will be con-
     catenated to the first, and vice-versa.  After the connection has been set 
up, nc does not really care
     which side is 
being used as 
a ??server?ˉ and which side is 
being used as 
a ??client?ˉ.  The connection may
     be terminated using 
an EOF (??^D?ˉ).
 
DATA TRANSFER
     The example in 
the previous section can be expanded to build a basic data transfer model.  Any infor-
     mation input into 
one end of the connection will be output to the other end, and input and output can
     be easily captured in 
order to emulate file transfer.
 
     Start by 
using nc to listen on 
a specific port, with output captured into 
a file:
 
           $ nc -l 1234 > filename.out
 
     Using a second machine, connect to the listening nc process, feeding it the file which is 
to be trans-
     ferred:
 
           $ nc host.example.com 1234 < filename.in
 
     After the file has been transferred, the connection will close automatically.
 
TALKING TO SERVERS
     It is 
sometimes useful to talk to servers ?°by 
hand?± rather than through a user interface.  It can aid
     in 
troubleshooting, when it might be necessary to verify what data a server is 
sending in 
response to
     commands issued by 
the client.  For example, to retrieve the home page of a web site:
 
           $ echo -n "GET / HTTP/1.0\r\n\r\n" 
| nc host.example.com 80
 
     Note that this 
also displays the headers sent by 
the web server.  They can be filtered, using 
a tool
     such as 
sed(1), if 
necessary.
 
     More complicated examples can be built up when the user knows the format of requests required by 
the
     server.  As another example, an email may be submitted to an SMTP server using:
 
           $ nc localhost 25 << EOF
           HELO host.example.com
           MAIL FROM: <user@host.example.com>
           RCPT TO: <user2@host.example.com>
           DATA
           Body of email.
           .
           QUIT
           EOF
 
PORT SCANNING
     It may be useful to know which ports are open and running services on 
a target machine.  The -z flag
     can be used to tell nc to report open ports, rather than initiate a connection.  For example:
 
           $ nc -z host.example.com 20-30
           Connection to host.example.com 22 port [tcp/ssh] succeeded!
           Connection to host.example.com 25 port [tcp/smtp] succeeded!
 
     The port range was specified to limit the search to ports 20 - 30.
 
     Alternatively, it might be useful to know which server software is 
running, and which versions.  This
     information is 
often contained within the greeting banners.  In order to retrieve these, it is 
neces-
     sary to first make a connection, and then break 
the connection when the banner has been retrieved.
     This can be accomplished by 
specifying a small timeout with the -w flag, or perhaps by 
issuing a
     "QUIT" 
command to the server:
 
           $ echo "QUIT" 
| nc host.example.com 20-30
           SSH-1.99-OpenSSH_3.6.1p2
           Protocol mismatch.
           220 host.example.com IMS SMTP Receiver Version 0.84 Ready
 
EXAMPLES
     Open a TCP connection to port 42 of host.example.com, using 
port 31337 as 
the source port, with a
     timeout of 5 seconds:
 
   <strong>        $ nc -p 31337 -w 5 host.example.com 42</strong>
 
     Open a UDP connection to port 53 of host.example.com:
 
         <strong>  $ nc -u host.example.com 53
</strong>
     Open a TCP connection to port 42 of host.example.com using 
10.1.2.3 as 
the IP for 
the local end of the
     connection:
 
           $ nc -s 10.1.2.3 host.example.com 42
 
     Create and listen on 
a Unix Domain Socket:
 
           $ nc -lU /var/tmp/dsocket
 
     Connect to port 42 of host.example.com via an HTTP proxy at 10.2.3.4, port 8080.  This example could
     also be used by 
ssh(1); see the ProxyCommand directive in 
ssh_config(5) for 
more information.
 
           $ nc -x10.2.3.4:8080 -Xconnect host.example.com 42
 
SEE ALSO
     cat(1), ssh(1)
 
AUTHORS
     Original implementation by 
*Hobbit* ?′hobbit@avian.org?μ.
     Rewritten with IPv6 support by 
Eric Jackson ?′ericj@monkey.org?μ.
 
CAVEATS
     UDP port scans will always succeed (i.e. report the port as 
open), rendering the -uz combination of
     flags relatively useless.
 
BSD

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