P4
ADDITIONAL SYSTEM INFORMATION :
Windows 10, OpenJDK 17
A DESCRIPTION OF THE PROBLEM :
Microsoft Windows 8+ has a socket backlog limit of 200. To override this limit, you need to pass a negative value, e.g., -500, to Win32 API listen(). However, from Java this is impossible, as non-positive backlog values are always overridden to 50.
This can be see here in OpenJDK17: sun.nio.ch.ServerSocketChannelImpl.bind(): Net.listen(fd, backlog < 1 ? 50 : backlog);
And here: java.net.ServerSocket.bind(java.net.SocketAddress, int): if (backlog < 1) backlog = 50;
Win32 API docs for listen() introduce the C macro SOMAXCONN_HINT() to specify very large socket backlog sizes. The C macro SOMAXCONN_HINT() defined in WinSock2.h. Looking at the macro definition, you can see that it simply negates the value. I wrote sample code to demonstrate very large backlog sizes can be created from Java using a negative backlog size during socket listen.
The "override to 50" is probably ancient behaviour and cannot be changed without breaking some existing code in the wild. (See: https://xkcd.com/1172/) Ideas: (1) Can you either add notes to the Java doc about this issue, or (2) add a new bind() method that allows negative backlog sizes? As a workaround, I wrote a custom impl of bind() that calls the JNI listen method directly with a negative backlog size. I confirm that a very large backlog (>200) is possible on Windows from Java.
More details here: https://stackoverflow.com/questions/78365010/how-to-set-java-server-socket-backlog-to-a-negative-value-on-windows
Windows 10, OpenJDK 17
A DESCRIPTION OF THE PROBLEM :
Microsoft Windows 8+ has a socket backlog limit of 200. To override this limit, you need to pass a negative value, e.g., -500, to Win32 API listen(). However, from Java this is impossible, as non-positive backlog values are always overridden to 50.
This can be see here in OpenJDK17: sun.nio.ch.ServerSocketChannelImpl.bind(): Net.listen(fd, backlog < 1 ? 50 : backlog);
And here: java.net.ServerSocket.bind(java.net.SocketAddress, int): if (backlog < 1) backlog = 50;
Win32 API docs for listen() introduce the C macro SOMAXCONN_HINT() to specify very large socket backlog sizes. The C macro SOMAXCONN_HINT() defined in WinSock2.h. Looking at the macro definition, you can see that it simply negates the value. I wrote sample code to demonstrate very large backlog sizes can be created from Java using a negative backlog size during socket listen.
The "override to 50" is probably ancient behaviour and cannot be changed without breaking some existing code in the wild. (See: https://xkcd.com/1172/) Ideas: (1) Can you either add notes to the Java doc about this issue, or (2) add a new bind() method that allows negative backlog sizes? As a workaround, I wrote a custom impl of bind() that calls the JNI listen method directly with a negative backlog size. I confirm that a very large backlog (>200) is possible on Windows from Java.
More details here: https://stackoverflow.com/questions/78365010/how-to-set-java-server-socket-backlog-to-a-negative-value-on-windows