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UrsPahoMqttClient心跳问题解决——Paho底层已自动处理，设好KeepAlive就行...
问一下心跳PingReq报文怎么发的
目的为保持 MQTT 连接，否则会被踢下线。
用的是什么MQTT扩展？UrsPahoMqttClient。
结论：不需要手动发心跳，Paho底层已内置实现
UrsPahoMqttClient 封装的是 Eclipse Paho MQTT 客户端，心跳（PingReq）...
Convert String to Uri
... to its standards. For example, try to parse: http://www.google.com/search?q=cat|dog. An exception will be thrown for the vertical bar.
urllib makes it easy to convert a string to a java.net.URI. It will pre-process and escape the URL.
assertEquals("http://www.google.com/search?q=cat%7Cdog",
...
How to select from subquery using Laravel Query Builder?
...y there is no method to create subquery in FROM clause, so you need to manually use raw statement, then, if necessary, you will merge all the bindings:
$sub = Abc::where(..)->groupBy(..); // Eloquent Builder instance
$count = DB::table( DB::raw("({$sub->toSql()}) as sub") )
->mergeBin...
What is the difference between static_cast and C style casting?
...runtime.
Also, c++ style casts can be searched for easily, whereas it's really hard to search for c style casts.
Another big benefit is that the 4 different C++ style casts express the intent of the programmer more clearly.
When writing C++ I'd pretty much always use the C++ ones over the the C...
Insert a line at specific line number with sed or awk
...
mac users: with homebrew, brew install gnu-sed and then use this with gsed
– cwd
Jan 10 '15 at 17:58
4
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Reading value from console, interactively
...locking on input, something node.js doesn't like to do.
Instead set up a callback to be called each time something is entered:
var stdin = process.openStdin();
stdin.addListener("data", function(d) {
// note: d is an object, and when converted to a string it will
// end with a linefeed. ...
Programmatically access currency exchange rates [closed]
... this, is there any information on what the parameters stand for? Specifically the "f" parameter. I can't find any info anywhere.
– Fishcake
Oct 8 '09 at 6:12
9
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Regular Expressions: Is there an AND operator?
...
It should be mentioned that this particular example is called a positive lookahead assertion. It has other uses than "and". Note that the text isn't consumed.
– strager
Jan 22 '09 at 21:11
...
How do I use a file grep comparison inside a bash if/else statement?
...tus is 0 if any line was selected, 1 otherwise;
if any error occurs and -q was not given, the exit status is 2.
if grep --quiet MYSQL_ROLE=master /etc/aws/hosts.conf; then
echo exists
else
echo not found
fi
You may want to use a more specific regex, such as ^MYSQL_ROLE=master$, to avoid th...
How to get the first non-null value in Java?
... the efficiency reasons that i mentioned above is that an array allocation will happen each time you invoke the var arg version of the method. this could be wasteful for hand-fulls of items, which i suspect will be common usage.
– les2
May 4 '10 at 1...