翻译：netcat manual

因为最近在搭建服务器要用到nc，所以阅读手册的同时也顺便把它翻译了，我的英语不好，如果哪里翻译错了，请指正。

 

NC(1) BSD General Commands Manual NC(1)

NAME
nc — arbitrary TCP and UDP connections and listens

SYNOPSIS
nc [-46DdhklnrStUuvzC] [-i interval] [-P proxy_username] [-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.
nc(或netcat)是用于在阳光下做的，任何涉及TCP或UDP的事情的实用性工具。它可以打开TCP连接，发送UDP数据包，监听任意的TCP和UDP端口，进行端口扫描，以及处理IPv4和IPv6。不同于telnet，nc的脚本非常好，而且分离错误信息到标准错误（stderr），而不是把它们发送到标准输出（stdout），比如telnet确实如此。

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.
强制nc只使用IPv4

-6 Forces nc to use IPv6 addresses only.
强制nc只使用IPv6

-D Enable debugging on the socket.
在socket上启用调试

-d Do not attempt to read from stdin.
不从标准输入上读取

-h Prints out nc help.
打印出nc的帮助提示

-i interval
Specifies a delay time interval between lines of text sent and received. Also causes a delay time between connections to multiple
ports.
指定文本行发送和接收的时间间隔。这也会导致多端口之间的连接延迟。

-k Forces nc to stay listening for another connection after its current connection is completed. It is an error to use this option with‐
out the -l option.
强制nc完成当前连接之后继续监听另一个连接。此选项必须与-l选项一起使用，否则将发生错误。

-l Used to specify that nc should listen for an incoming connection rather than initiate a connection 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.
用于指定nc应该监听一个接入连接，而不是启动连接到一个远程主机。此选项结合-p,-s,或-z选项会发生错误。此外，-w指定的超时会被忽略。

-n Do not do any DNS or service lookups on any specified addresses, hostnames or ports.
任何指定地址，主机名或端口都不做DNS或(其他)服务查找。

-P proxy_username
Specifies a username to present to a proxy server that requires authentication. If no username is specified then authentication will
not be attempted. Proxy authentication is only supported for HTTP CONNECT proxies at present.
指定一个用户名给要求身份验证的代理服务器。如果没有指定用户名将不会尝试身份验证。目前只支持HTTP CONNECT代理身份验证。

-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.
指定nc应使用的源端口，受权限限制和其可用性的影响。此选项结合-l会发生错误。

-q after EOF on stdin, wait the specified number of seconds and then quit. If seconds is negative, wait forever.
标准输入遇到EOF之后，等待指定秒数然后退出。如果秒数是负的，将会永远等待下去。

-r Specifies that source and/or destination ports should be chosen randomly instead of sequentially within a range or in the order that
the system assigns them.
指定源端口和/或目标端口应该随机选择，而不是按照一个范围内的顺序或系统分配的顺序。

-S Enables the RFC 2385 TCP MD5 signature option.
启用RFC 2385 TCP MD5签名。（不懂）

-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.
指定用于发送数据包的接口IP。结合-l选项一起使用会发生错误。

-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”.
指定连接IP的服务类型（TOS）。有效值是"lowdelay","throughput","reliability"令牌，或者是以"0x"开头的8位十六进制值

-C Send CRLF as line-ending
发送CRLF作为行结束符。

-t Causes nc to send RFC 854 DON'T and WON'T responses to RFC 854 DO and WILL requests. This makes it possible to use nc to script tel‐
net sessions.

-U Specifies to use Unix Domain Sockets.
指定使用Unix套接字
-u Use UDP instead of the default option of TCP.
使用UDP协议而不是默认使用TCP协议。

-v Have nc give more verbose output.
使nc得到更详细的输出。

-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.
如果连接或标准输入闲置超过timeout秒以上，那么连接将自动关闭。-w不会影响-l选项，即无论带不带-w选项，nc都会永远监听连接。默认情况下没有设置timeout。

-X proxy_protocol
Requests that nc should use the specified protocol when talking to the proxy server. Supported 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.
要求nc使用指定协议与代理服务器交互。支持的协议有："4"(SOCKS v.4), "5"(SOCK v.5), 和"connect"(HTTPS proxy)。如果没有指定，默认使用SOCK v.5

-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).
nc使用porxy_address[:port]代理连接到主机。如果没有指定端口，就使用协议对应的众所周知的端口（如SOCKS:1080，HTTPS:3128）。

-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 con‐
junction with the -l option.
nc只扫描（目标机器的）正在监听的守护进程，且在不会发送任何数据给他们。此选项结合-l选项会发生错误。

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).
hostname可以是一个数字IP地址或字符主机名（除非使用-n选项）。正常情况下，hostname必须指定，除非使用了-l选项（这种情况下，则使用本地主机）。

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).
端口号可以是单个整数或者是一个范围。使用范围的形式:nn-mm。一般情况下，必须指定一个目标端口，除非使用-U选项（这种情况下必须指定socket）。

CLIENT/SERVER MODEL
客户端/服务器 模式
It is quite simple to build a very basic client/server model using nc. On one console, start nc listening on a specific port for a connec‐
tion. For example:
用nc非常简单的建立一个基本的客户端/服务器模式。在一个控制台中，启动nc监听一个指定端口的连接。

$ 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此时正在监听1234端口上的连接。在另一个控制台上（或者另一台机器），连接到此机器和端口的连接会被监听。

$ nc 127.0.0.1 1234

There should now be a connection between the ports. Anything typed at the second console will be concatenated 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’ and which side is being used as a
‘client’. The connection may be terminated using an EOF (‘^D’).
现在应该有端口间的连接。在第二个控制台上输入的任何内容都会被串联到第一个控制台，反之亦然。连接建立之后，nc不会真正关心哪一边作为“服务器”，哪一边作为“客户端”。可以使用一个EOF('^D')来终止连接。

DATA TRANSFER
数据传输
The example in the previous section can be expanded to build a basic data transfer model. Any information input into one end of the connec‐
tion will be output to the other end, and input and output can be easily captured in order to emulate file transfer.
上一节的例子可以扩展到建立一个基本的数据传输模式。任何信息从连接的一端输入，会在另一端被输出，为了模拟文件传输，输入和输出可以很容易被捕捉到。

Start by using nc to listen on a specific port, with output captured into a file:
首先启动nc监听一个指定的端口，把捕捉到的信息输出到一个文件：

$ nc -l 1234 > filename.out

Using a second machine, connect to the listening nc process, feeding it the file which is to be transferred:
使用另一台机器，连接到nc监听进程，输入一个要传输的文件：

$ nc host.example.com 1234 < filename.in

After the file has been transferred, the connection will close automatically.
文件传输完毕后，此连接会自动关闭。

TALKING TO SERVERS
与服务器交互
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:
有时“通过手”而不是通过一个用户接口与服务器交互是很有好处的。当需要验证服务器发送的数据以响应客户端发出的命令时，这样可以帮助我们进行排除故障。
例如，检索一个网站的主页：

$ 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.
请注意，这也显示了web服务器发送的消息头。如果有必要，可以使用诸如sed这样的工具把它们过滤掉。

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:
当用户知道服务器所需的请求的格式时，可以建立更复杂的例子。另一个例子，一封电子邮件可能被提交到SMTP服务器使用：

$ nc [-C] 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
端口扫描
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:
对于想知道目标机器上开放的端口和运行的服务，这可能会有用。-z选项可用于告诉nc返回（目标机器）开放的端口，而不是发起一个连接。例如：

$ 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.
指定一个端口范围，将端口搜索范围限制在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 necessary 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:
或者，用于获取（目标机器指定端口）有哪些服务软件正在运行，和（软件的）版本信息。这些信息通常包含在欢迎信息内。为了获取这些信息，必须先建立一个连接，然后在获取到欢迎信息时关闭连接。可以通过-w选项指定一个小延时，或者给服务器发送一个“QUIT”命令来实现。

$ 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:
打开一个TCP连接到host.example.com的42端口，使用31337作为源端口，以及5秒的超时：

$ nc -p 31337 -w 5 host.example.com 42

Open a UDP connection to port 53 of host.example.com:
打开一个UDP连接到host.example.com的53端口:

$ nc -u host.example.com 53

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:
打开一个TCP连接到host.example.com的42端口，使用10.1.2.3 IP作为本地端连接：

$ nc -s 10.1.2.3 host.example.com 42

Create and listen on a Unix Domain Socket:
在Unix Domain Socket上创建并监听：

$ 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.
通过代理服务器10.2.3.4的8080端口连接到host.exzmple.com的42端口。这个例子也可用于ssh；详细的信息请查看ssh_config的ProxyCommand指令。

$ nc -x10.2.3.4:8080 -Xconnect host.example.com 42

The same example again, this time enabling proxy authentication with username “ruser” if the proxy requires it:
同样的例子，这次启用代理身份认证，使用用户名“ruser”，如果代理服务器需要(认证)。

$ nc -x10.2.3.4:8080 -Xconnect -Pruser host.example.com 42

SEE ALSO
cat(1), ssh(1)

AUTHORS
Original implementation by *Hobbit* ⟨hobbit@avian.org⟩.
Rewritten with IPv6 support by Eric Jackson ⟨ericj@monkey.org⟩.

CAVEATS
UDP port scans will always succeed (i.e. report the port as open), rendering the -uz combination of flags relatively useless.

BSD March 23, 2013 BSD