asio | boost asio学习实践记录 | SDK library

I've found a related question where the same author found the solution, please click here to see:

As a side note, if you have the same error, and provided solutions does not work, please, follow the link and try this answer,but paying special attention to remove both lib and log files created by mongodb,

The problem is your getData function returns undefined. Though starts an axios request in 'backround'. And your test case calls it and immediatelly proceeds to the next line (expect(login == true)).

To fix it you should make the getData function return created by axios.get promise. And add await before getData call in test case to wait for it to finish.

You can buffer the data and extract whole messages when the separator is found. Example:

server.py

This is what I meant with this comment

though boost::system::system_error could invite issues back

The trouble is, error categories are global singleton instances, with object identity (i.e. compared for equality by their address).

You'r ending up with multiple instances in multiple modules. The usual solution is to

• dynamically link to Boost System, so all libraries use the same copy (this does however sometimes run into initialization order issues)
• if that doesn't solve it, make sure all modules actually load the same library (version?)
• In recent boosts I think there's the option to build Boost System completely header-only. This may or may not involve new-fangled C++14 inline, I haven't checked.

If all else fails, do your own translation. There's related issues that might give you ideas:

• Is it possible to convert a boost::system::error_code to a std:error_code?
• Do note that exceptions may run into very similar issues due to RTTI not necessarily matching; exceptions need to be exported types and linked dynamically from the same module for the exception handlers to match the thrown runtime type id.

Is it normal or expected to compare only errorCode.value() against enums?

No it is not. According to some sources Boost as well as standard library promise to map generic error category to errc which is standard - so you could do that, but you still have to figure out whether that is the category, so doesn't help your scenario.

digging into the sources of boost::asio::awaitable, I figured out that I just should make use of co_return keyword. Surprisingly, it is not shipped with boost. It is enabled either by -fcoroutines flag or -std=c++20. Unexpectedly. Having said that, it is solved.

The error triggers when you so s.remote_endpoint on a socket that is not connected/no longer connected.

It would happen e.g. when you try to print the endpoint with the socket after an IO error. The usual way to work around that is to store a copy of the remote endpoint as soon as a connection is established, so you don't have to retrieve it when it's too late.

On the question why it's happening on the particular VM, you have to shift focus to the root cause. It might be that accept is failing (possibly due to limits like number of filedescriptors, available memory, etc.)

Use zmq_msg_init_data

http://api.zeromq.org/master:zmq-msg-init-data

You can provide the memory pointer/size of your already allocated memory and zeromq will take ownership (skipping the extra allocation). Once its been processed and is no longer needed it will call the associated free function where your own code can clean up.

I have used this approach in the past with a memory pool/ circular buffer and it worked well.

In general, you can’t do this because the type of the parameter conn is determined elsewhere, by code that might in some cases be declared after this class is defined. If the function accepting the callback returns something whose type is based on the type the callback returns, you can write something like decltype(reqOp.reqOp(…,[](auto x) {return x;})), but otherwise the information about what type was passed is lost. (There are stateful metaprogramming tricks that might be used to exfiltrate the information with a similar trick, but they’re best avoided.)