测试是否从Shell脚本打开了远程TCP端口

太过爱你忘了你带给我的痛 2022-11-25 13:06 256阅读 0赞

本文翻译自：[Test if remote TCP port is open from a shell script][]

*I'm looking for a quick and simple method for properly testing if a given TCP port is open on a remote server, from inside a Shell script.* **我正在寻找一种快速，简单的方法来从Shell脚本内部正确测试远程服务器上是否打开了给定的TCP端口。**

*I've managed to do it with the telnet command, and it works fine when the port is opened, but it doesn't seem to timeout when it's not and just hangs there...* **我已经用telnet命令做到了，当打开端口时，它可以正常工作，但是当端口不打开时，它似乎并没有超时，而只是挂在那里。**

*Here's a sample:* **这是一个示例：**

l_TELNET=`echo "quit" | telnet $SERVER $PORT | grep "Escape character is"`
    if [ "$?" -ne 0 ]; then
      echo "Connection to $SERVER on port $PORT failed"
      exit 1
    else
      echo "Connection to $SERVER on port $PORT succeeded"
      exit 0
    fi

*I either need a better way, or a way to force telnet to timeout if it doesn't connect in under 8 seconds for example, and return something I can catch in Shell (return code, or string in stdout).* **我或者需要一种更好的方法，或者是一种强制telnet超时的方法（例如，如果它在8秒内没有连接），然后返回我可以在Shell中捕获的内容（返回代码或stdout中的字符串）。**

*I know of the Perl method, which uses the IO::Socket::INET module and wrote a successful script that tests a port, but would rather like to avoid using Perl if possible.* **我知道Perl方法，该方法使用IO :: Socket :: INET模块并编写了成功的脚本来测试端口，但如果可能的话，希望避免使用Perl。**

*Note: This is what my server is running (where I need to run this from)* **注意：这就是我的服务器正在运行的（我需要从中运行）**

*SunOS 5.10 Generic\_139556-08 i86pc i386 i86pc* **SunOS 5.10 Generic\_139556-08 i86pc i386 i86pc**

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### \#1楼 ###

参考：[https://stackoom.com/question/kEGj/测试是否从Shell脚本打开了远程TCP端口][https_stackoom.com_question_kEGj_Shell_TCP]

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### \#2楼 ###

## *TOC:* **目录：** ##

*  *Using bash and `timeout`* **使用bash和`timeout`**
    
     *  *Command* **命令**
     *  *Examples* **例子**
 *  *Using `nc`* **使用`nc`**
    
     *  *Command* **命令**
     *  *RHEL 6 (nc-1.84)* **RHEL 6（nc-1.84）**
        
         *  *Installation* **安装**
         *  *Examples* **例子**
     *  *RHEL 7 (nmap-ncat-6.40)* **RHEL 7（nmap-ncat-6.40）**
        
         *  *Installation* **安装**
         *  *Examples* **例子**
 *  *Remarks* **备注**

# *Using bash and `timeout` :* **使用bash和`timeout` ：** #

*Note that `timeout` should be present with RHEL 6+, or is alternatively found in GNU coreutils 8.22.* **请注意， `timeout`应该在RHEL 6+中出现，或者可以在GNU coreutils 8.22中找到。** *On MacOS, install it using `brew install coreutils` and use it as `gtimeout` .* **在MacOS上，使用`brew install coreutils`安装它，并将其用作`gtimeout` 。**

## *Command:* **命令：** ##

$ timeout $TIMEOUT_SECONDS bash -c "</dev/tcp/${HOST}/${PORT}"; echo $?

*If parametrizing the host and port, be sure to specify them as `${HOST}` and `${PORT}` as is above.* **如果对主机和端口进行参数设置，请确保如上所述将它们指定为`${HOST}`和`${PORT}` 。** *Do not specify them merely as `$HOST` and `$PORT` , ie without the braces;* **不要仅将它们指定为`$HOST`和`$PORT` ，即不使用大括号；** *it won't work in this case.* **在这种情况下将不起作用。**

## *Example:* **例：** ##

### *Success:* **成功：** ###

$ timeout 2 bash -c "</dev/tcp/canyouseeme.org/80"; echo $?
    0

### *Failure:* **失败：** ###

$ timeout 2 bash -c "</dev/tcp/canyouseeme.org/81"; echo $?
    124

*If you must preserve the exit status of `bash` ,* **如果您必须保留`bash`的退出状态，**

$ timeout --preserve-status 2 bash -c "</dev/tcp/canyouseeme.org/81"; echo $?
    143

# *Using `nc` :* **使用`nc` ：** #

*Note that a backward incompatible version of `nc` gets installed on RHEL 7.* **请注意，RHEL 7上安装了向后不兼容的`nc`版本。**

## *Command:* **命令：** ##

*Note that the command below is unique in that it is identical for both RHEL 6 and 7. It's just the installation and output that are different.* **请注意，以下命令是唯一的，因为它对于RHEL 6和7是相同的。只是安装和输出是不同的。**

$ nc -w $TIMEOUT_SECONDS -v $HOST $PORT </dev/null; echo $?

## *RHEL 6 (nc-1.84):* **RHEL 6（nc-1.84）：** ##

### *Installation:* **安装：** ###

$ sudo yum install nc

### *Examples:* **例子：** ###

*Success:* **成功：**

$ nc -w 2 -v canyouseeme.org 80 </dev/null; echo $? Connection to canyouseeme.org 80 port [tcp/http] succeeded! 0

*Failure:* **失败：**

$ nc -w 2 -v canyouseeme.org 81 </dev/null; echo $? nc: connect to canyouseeme.org port 81 (tcp) timed out: Operation now in progress 1

*If the hostname maps to multiple IPs, the above failing command will cycle through many or all of them.* **如果主机名映射到多个IP，则上面失败的命令将在许多或所有IP中循环。** *For example:* **例如：**

$ nc -w 2 -v microsoft.com 81 </dev/null; echo $? nc: connect to microsoft.com port 81 (tcp) timed out: Operation now in progress nc: connect to microsoft.com port 81 (tcp) timed out: Operation now in progress nc: connect to microsoft.com port 81 (tcp) timed out: Operation now in progress nc: connect to microsoft.com port 81 (tcp) timed out: Operation now in progress nc: connect to microsoft.com port 81 (tcp) timed out: Operation now in progress 1

## *RHEL 7 (nmap-ncat-6.40):* **RHEL 7（nmap-ncat-6.40）：** ##

### *Installation:* **安装：** ###

$ sudo yum install nmap-ncat

### *Examples:* **例子：** ###

*Success:* **成功：**

$ nc -w 2 -v canyouseeme.org 80 </dev/null; echo $? Ncat: Version 6.40 ( http://nmap.org/ncat ) Ncat: Connected to 52.202.215.126:80. Ncat: 0 bytes sent, 0 bytes received in 0.22 seconds. 0

*Failure:* **失败：**

$ nc -w 2 -v canyouseeme.org 81 </dev/null; echo $? Ncat: Version 6.40 ( http://nmap.org/ncat ) Ncat: Connection timed out. 1

$ nc -w 2 -v microsoft.com 81 </dev/null; echo $? Ncat: Version 6.40 ( http://nmap.org/ncat ) Ncat: Connection to 104.43.195.251 failed: Connection timed out. Ncat: Trying next address... Ncat: Connection to 23.100.122.175 failed: Connection timed out. Ncat: Trying next address... Ncat: Connection to 23.96.52.53 failed: Connection timed out. Ncat: Trying next address... Ncat: Connection to 191.239.213.197 failed: Connection timed out. Ncat: Trying next address... Ncat: Connection timed out. 1

# *Remarks:* **备注：** #

*The `-v` ( `--verbose` ) argument and the `echo $?`* **`-v` （-- `--verbose` ）参数和`echo $?`** *command are of course for illustration only.* **命令当然仅用于说明。**

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### \#3楼 ###

*If you're using **ksh** or **bash** they both support IO redirection to/from a socket using the **/dev/tcp/IP/PORT** construct.* **如果您使用的是ksh或bash，它们都支持使用/ dev / tcp / IP / PORT构造从IO重定向到套接字或从套接字重定向。** *In this **Korn shell** example I am redirecting no-op's ( **:** ) std-in from a socket:* **在此Korn shell示例中，我从套接字重定向no-op的（ ： ）std-in：**

W$ python -m SimpleHTTPServer &
    [1]     16833
    Serving HTTP on 0.0.0.0 port 8000 ...
    W$ : </dev/tcp/127.0.0.1/8000

*The shell prints an error if the socket is not open:* **如果套接字未打开，则外壳会显示错误：**

W$ : </dev/tcp/127.0.0.1/8001
    ksh: /dev/tcp/127.0.0.1/8001: cannot open [Connection refused]

*You can therefore use this as the **test** in an **if** condition:* **因此，可以在if条件下将此作为测试 ：**

SERVER=127.0.0.1 PORT=8000
    if (: < /dev/tcp/$SERVER/$PORT) 2>/dev/null
    then
        print succeeded
    else
        print failed
    fi

*The no-op is in a subshell so I can throw std-err away if the std-in redirection fails.* **no-op位于子外壳中，因此如果std-in重定向失败，我可以丢弃std-err。**

*I often use **/dev/tcp** for checking the availability of a resource over HTTP:* **我经常使用/ dev / tcp通过HTTP检查资源的可用性：**

W$ print arghhh > grr.html
    W$ python -m SimpleHTTPServer &
    [1]     16863
    Serving HTTP on 0.0.0.0 port 8000 ...
    W$ (print -u9 'GET /grr.html HTTP/1.0\n';cat <&9) 9<>/dev/tcp/127.0.0.1/8000
    HTTP/1.0 200 OK
    Server: SimpleHTTP/0.6 Python/2.6.1
    Date: Thu, 14 Feb 2013 12:56:29 GMT
    Content-type: text/html
    Content-Length: 7
    Last-Modified: Thu, 14 Feb 2013 12:55:44 GMT
    
    arghhh
    W$

*This one-liner opens **file descriptor 9** for reading from and writing to the socket, prints the **HTTP GET** to the socket and uses **`cat`** to read from the socket.* **这个单行代码打开文件描述符9以便从套接字读取和写入套接字，将HTTP GET打印到套接字，并使用`cat`从套接字读取。**

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### \#4楼 ###

*It's easy enough to do with the `-z` and `-w TIMEOUT` options to `nc` , but not all systems have `nc` installed.* **使用`nc`的`-z`和`-w TIMEOUT`选项非常容易，但是并非所有系统都安装了`nc` 。** *If you have a recent enough version of bash, this will work:* **如果您的bash版本足够新，则可以使用：**

# Connection successful:
    $ timeout 1 bash -c 'cat < /dev/null > /dev/tcp/google.com/80'
    $ echo $?
    0
    
    # Connection failure prior to the timeout
    $ timeout 1 bash -c 'cat < /dev/null > /dev/tcp/sfsfdfdff.com/80'
    bash: sfsfdfdff.com: Name or service not known
    bash: /dev/tcp/sfsfdfdff.com/80: Invalid argument
    $ echo $?
    1
    
    # Connection not established by the timeout
    $ timeout 1 bash -c 'cat < /dev/null > /dev/tcp/google.com/81'
    $ echo $?
    124

*What's happening here is that `timeout` will run the subcommand and kill it if it doesn't exit within the specified timeout (1 second in the above example).* **这里发生的是，如果超时未在指定的超时时间内退出（在上面的示例中为1秒），则`timeout`将运行子命令并将其杀死。** *In this case `bash` is the subcommand and uses its special [/dev/tcp handling][dev_tcp handling] to try and open a connection to the server and port specified.* **在这种情况下， `bash`是子命令，并使用其特殊的[/ dev / tcp处理][dev_tcp handling]来尝试打开与指定服务器和端口的连接。** *If `bash` can open the connection within the timeout, `cat` will just close it immediately (since it's reading from `/dev/null` ) and exit with a status code of `0` which will propagate through `bash` and then `timeout` .* **如果`bash`可以在超时内打开连接，则`cat`会立即将其关闭（因为它正在从`/dev/null`读取），并以状态代码`0`退出，该状态代码将通过`bash`传播，然后`timeout` 。** *If `bash` gets a connection failure prior to the specified timeout, then `bash` will exit with an exit code of 1 which `timeout` will also return.* **如果`bash`在指定的超时之前连接失败，则`bash`将以退出代码1退出，该`timeout`代码也将返回。** *And if bash isn't able to establish a connection and the specified timeout expires, then `timeout` will kill `bash` and exit with a status of 124.* **如果bash无法建立连接并且指定的超时时间到期，则`timeout`将杀死`bash`并以124状态退出。**

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### \#5楼 ###

*While an old question, I've just dealt with a variant of it, but none of the solutions here were applicable, so I found another, and am adding it for posterity.* **虽然这是一个老问题，但我只是处理了它的一个变体，但这里没有一个适用的解决方案，因此我找到了另一个解决方案，并将其添加以供后代使用。** *Yes, I know the OP said they were aware of this option and it didn't suit them, but for anyone following afterwards it might prove useful.* **是的，我知道OP表示他们知道此选项，因此不适合他们，但是对于之后的所有人来说，它可能会有用。**

*In my case, I want to test for the availability of a local `apt-cacher-ng` service from a `docker` build.* **就我而言，我想从`docker`构建中测试本地`apt-cacher-ng`服务的可用性。** *That means absolutely nothing can be installed prior to the test.* **这意味着在测试之前绝对不能安装任何东西。** *No `nc` , `nmap` , `expect` , `telnet` or `python` .* **没有`nc` ， `nmap` ， `expect` ， `telnet`或`python` 。** *`perl` however is present, along with the core libraries, so I used this:* **但是， `perl`与核心库一起存在，因此我使用了以下代码：**

perl -MIO::Socket::INET -e 'exit(! defined( IO::Socket::INET->new("172.17.42.1:3142")))'

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### \#6楼 ###

*I needed short script which was run in cron and hasn't output.* **我需要在cron中运行且没有输出的简短脚本。** *I solve my trouble using nmap* **我使用nmap解决了我的麻烦**

open=`nmap -p $PORT $SERVER | grep "$PORT" | grep open`
    if [ -z "$open" ]; then
      echo "Connection to $SERVER on port $PORT failed"
      exit 1
    else
      echo "Connection to $SERVER on port $PORT succeeded"
      exit 0
    fi

*To run it You should install nmap because it is not default installed package.* **要运行它，您应该安装nmap，因为它不是默认安装的软件包。**

[Test if remote TCP port is open from a shell script]: https://oldbug.net/q/kEGj/Test-if-remote-TCP-port-is-open-from-a-shell-script
[https_stackoom.com_question_kEGj_Shell_TCP]: https://stackoom.com/question/kEGj/%E6%B5%8B%E8%AF%95%E6%98%AF%E5%90%A6%E4%BB%8EShell%E8%84%9A%E6%9C%AC%E6%89%93%E5%BC%80%E4%BA%86%E8%BF%9C%E7%A8%8BTCP%E7%AB%AF%E5%8F%A3
[dev_tcp handling]: http://www.tldp.org/LDP/abs/html/devref1.html#DEVTCP