bash 在响应中返回某个字符后，如何关闭 netcat 连接？
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How can I close a netcat connection after a certain character is returned in the response?
提问by SCdF
We have a very simple tcp messaging script that cats some text to a server port which returns and displays a response.
我们有一个非常简单的 tcp 消息传递脚本，它将一些文本发送到服务器端口，该端口返回并显示响应。
The part of the script we care about looks something like this:
我们关心的脚本部分看起来像这样：
cat someFile | netcat somehost 1234
The response the server returns is 'complete' once we get a certain character code (specifically &001C) returned.
一旦我们得到返回的某个字符代码（特别是&001C），服务器返回的响应就是“完整的” 。
How can I close the connection when I receive this special character?
当我收到这个特殊字符时如何关闭连接？
(Note: The server won'tclose the connection for me. While I currently just CTRL+C the script when I can tell it's done, I wish to be able to send many of these messages, one after the other.)
（注意：服务器不会为我关闭连接。虽然我目前只是 CTRL+C 脚本，当我知道它已经完成时，我希望能够一个接一个地发送这些消息中的许多。）
(Note: netcat -w xisn't good enough because I wish to push these messages through as fast as possible)
（注意：netcat -w x还不够好，因为我希望尽快推送这些消息）
回答by caf
Create a bash script called client.sh:
创建一个名为 client.sh 的 bash 脚本：
#!/bin/bash
cat someFile
while read FOO; do
echo $FOO >&3
if [[ $FOO =~ `printf ".*\x00\x1c.*"` ]]; then
break
fi
done
Then invoke netcat from your main script like so:
然后从您的主脚本调用 netcat ，如下所示：
3>&1 nc -c ./client.sh somehost 1234
(You'll need bash version 3 for the regexp matching).
（您需要 bash 版本 3 才能进行正则表达式匹配）。
This assumes that the server is sending data in lines - if not you'll have to tweak client.sh so that it reads and echoes a character at a time.
这假设服务器正在按行发送数据 - 如果不是，您将不得不调整 client.sh 以便它一次读取和回显一个字符。
回答by anishsane
How about this?
这个怎么样？
Client side:
客户端：
awk -v RS=$'\x1c' 'NR==1;{exit 0;}' < /dev/tcp/host-ip/port
Testing:
测试：
# server side test script
while true; do ascii -hd; done | { netcat -l 12345; echo closed...;}
# Generate 'some' data for testing & pipe to netcat.
# After netcat connection closes, echo will print 'closed...'
# Client side:
awk -v RS=J 'NR==1; {exit;}' < /dev/tcp/localhost/12345
# Changed end character to 'J' for testing.
# Didn't wish to write a server side script to generate 0x1C.
Client side produces:
客户端产生：
0 NUL 16 DLE 32 48 0 64 @ 80 P 96 ` 112 p
1 SOH 17 DC1 33 ! 49 1 65 A 81 Q 97 a 113 q
2 STX 18 DC2 34 " 50 2 66 B 82 R 98 b 114 r
3 ETX 19 DC3 35 # 51 3 67 C 83 S 99 c 115 s
4 EOT 20 DC4 36 $ 52 4 68 D 84 T 100 d 116 t
5 ENQ 21 NAK 37 % 53 5 69 E 85 U 101 e 117 u
6 ACK 22 SYN 38 & 54 6 70 F 86 V 102 f 118 v
7 BEL 23 ETB 39 ' 55 7 71 G 87 W 103 g 119 w
8 BS 24 CAN 40 ( 56 8 72 H 88 X 104 h 120 x
9 HT 25 EM 41 ) 57 9 73 I 89 Y 105 i 121 y
10 LF 26 SUB 42 * 58 : 74
After 'J' appears, server side closes & prints 'closed...', ensuring that the connection has indeed closed.
'J' 出现后，服务器端关闭并打印 'closed...'，确保连接确实已关闭。
回答by bdonlan
Try:
尝试：
(cat somefile; sleep $timeout) | nc somehost 1234 | sed -e '{s/\x01.*//;T skip;q;:skip}'
This requires GNU sed.
这需要GNU sed。
How it works:
这个怎么运作：
{
s/\x01.*//; # search for \x01, if we find it, kill it and the rest of the line
T skip; # goto label skip if the last s/// failed
q; # quit, printing current pattern buffer
:skip # label skip
}
Note that this assumes there'll be a newline after \x01 - sed won't see it otherwise, as sed operates line-by-line.
请注意，这假设 \x01 之后会有一个换行符 - 否则 sed 不会看到它，因为 sed 逐行运行。
回答by bdonlan
Maybe have a look at Ncat as well:
也许也看看 Ncat：
"Ncat is the culmination of many key features from various Netcat incarnations such as Netcat 1.x, Netcat6, SOcat, Cryptcat, GNU Netcat, etc. Ncat has a host of new features such as "Connection Brokering", TCP/UDP Redirection, SOCKS4 client and server supprt, ability to "Chain" Ncat processes, HTTP CONNECT proxying (and proxy chaining), SSL connect/listen support, IP address/connection filtering, plus much more."
“Ncat 是 Netcat 1.x、Netcat6、SOcat、Cryptcat、GNU Netcat 等各种 Netcat 版本的许多关键功能的结晶。Ncat 具有许多新功能，例如“连接代理”、TCP/UDP 重定向、 SOCKS4 客户端和服务器支持、“链接”Ncat 进程的能力、HTTP CONNECT 代理（和代理链接）、SSL 连接/侦听支持、IP 地址/连接过滤等等。”
回答by Gabriel Le Roux
This worked best for me. Just read the output with a while loop and then check for "0x1c" using an if statement.
这对我来说效果最好。只需使用 while 循环读取输出，然后使用 if 语句检查“0x1c”。
while read i; do
if [ "$i" = "0x1c" ] ; then # Read until "0x1c". Then exit
break
fi
echo $i;
done < <(cat someFile | netcat somehost 1234)
回答by tomheron
This works great:
这很好用：
echo ^C | nc -v 29.7.144.21 1364
See output below:
请参阅下面的输出：
[root@localhost ~]# echo ^C | nc -v 29.7.144.21 1364 Ncat: Version 6.40 ( http://nmap.org/ncat) Ncat: Connected to 29.7.144.21:1364. ^C Ncat: 3 bytes sent, 0 bytes received in 0.01 seconds.
[root@localhost ~]#
[root@localhost ~]# echo ^C | nc -v 29.7.144.21 1364 Ncat：版本 6.40 ( http://nmap.org/ncat) Ncat：连接到 29.7.144.21:1364。^C Ncat：发送 3 个字节，0.01 秒内接收 0 个字节。
[root@localhost ~]#
