bash 如何使用netcat等待开放端口？
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原文地址: http://stackoverflow.com/questions/27599839/
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How to wait for an open port with netcat?
提问by FXG
I'm trying to do a custom dockerfile with jenkins on it. I would to wait until port 8080 is open instead of doing an ugly 'sleep 60' with netcat but in not very confident with bash scripts and netcat.
我正在尝试使用 jenkins 做一个自定义的 dockerfile。我会等到端口 8080 打开，而不是用 netcat 做一个丑陋的“睡眠 60”，但对 bash 脚本和 netcat 不是很自信。
Here is an example of what i'm trying to do:
这是我正在尝试做的一个例子：
#!/bin/bash
opened=0
while [ "$opened" == "0" ]; do
echo "Waiting jenkins to launch on 8080..."
nc -vz localhost 8080
done
echo "Jenkins launched"
回答by user987339
You can't set netcat to wait until some port is open, so you have to add part for waiting before next check is made. Try this:
您不能将 netcat 设置为等到某个端口打开，因此您必须在下一次检查之前添加等待部分。尝试这个：
#!/bin/bash
echo "Waiting jenkins to launch on 8080..."
while ! nc -z localhost 8080; do
sleep 0.1 # wait for 1/10 of the second before check again
done
echo "Jenkins launched"
回答by Onlyjob
I suggest the following one liners:
我建议使用以下一种衬垫：
## netcat version:
timeout 22 sh -c 'until nc -z #!/bin/bash
echo "Waiting jenkins to launch on 8080..."
while ! timeout 1 bash -c "echo > /dev/tcp/localhost/8080"; do
sleep 1
done
echo "Jenkins launched"
; do sleep 1; done' stackoverflow.com 443
## pure bash version:
timeout 22 bash -c 'until printf "" 2>>/dev/null >>/dev/tcp/# without timeout
wait-port localhost:8080
# timeout after a minute
wait-port -t 60000 localhost:8080
/; do sleep 1; done' stackoverflow.com 443
Both commands exit as soon as connection is established, trying every second for up to 22 seconds.
一旦建立连接，这两个命令都会退出，每秒尝试一次，最多 22 秒。
Note that thanks to timeoutcommand exit code is 0when port is accessible otherwise 124(if no connection established within given time).
请注意，多亏了timeout命令退出代码0，否则端口可访问124（如果在给定时间内未建立连接）。
回答by Anthony O.
回答by Dave Kerr
I have found this a common enough problem to write a utility to wait for a port to open, with an optional timeout:
我发现这是一个足够常见的问题，可以编写一个实用程序来等待端口打开，并带有可选的超时：
$ waitport 3000
Connection to localhost port 3000 [tcp/hbci] succeeded!
It's open source and available at github.com/dwmkerr/wait-port. Hopefully others will find it useful!
它是开源的，可从github.com/dwmkerr/wait-port 获得。希望其他人会发现它有用！
回答by johntellsall
To expand on user987339's answer, here's how to easily wait for a port in your terminal:
要扩展 user987339 的回答，以下是在终端中轻松等待端口的方法：
waitport function
等待端口功能
Add this function to your ~/.bashrc setup file:
将此函数添加到您的 ~/.bashrc 安装文件中：
##代码##Log out then back in to load ~/.bashrc. Then, run this command to verify that port 3000 has a server listening to it:
注销然后重新登录以加载 ~/.bashrc。然后，运行此命令以验证端口 3000 是否有服务器侦听它：
##代码##This has been validated on macOS. It might not work on Fedora/CentOS, as they lack the -zoption for netcat.
这已在 macOS 上得到验证。它可能无法在Fedora / CentOS的工作，因为他们缺乏-z的选项netcat。
