How can I close a tcp/ip socket without killing the owning process?

Problem: a program has a socket open and you want to force it to close without killing the owning process.

Solution: get the file descriptor of the socket, debug the process and manually call close on the file descriptor.

On Linux systems:

1. Find the offending process: netstat -np
2. Find the socket file descriptor: lsof -np $PID
3. Debug the process: gdb -p $PID
4. Close the socket: call close($FD)
5. Close the debugger: quit
6. Profit.

From here.

On OSX the incantations are differently formed:

1. Find the offending process and file descriptor: lsof -ni TCP
2. Debug the process: lldb -p $PID
3. Close the socket: call (int)close($FD)
4. Close the debugger: quit
5. Profit.