listener.d: crashes upon unclean disconnect - exception

Question

For a small chat server thingie I'm making, I decided to use D; finding myself
with a very neat example from listener.d to get a kick start I decided to
pretty much take the example over! However, I'm stuck on a bug I can't truly
wrap my finger around. Most likely it's my own fault and I'm doing something
wrong, but considering I took the code pretty much from the example I am more
inclined to believe the example is broken.
I'll explain what happens:
List item
I start up my server (nothing wrong, it's running as it should and listening)
I telnet to it. My server accepts the connection.
I use telnet to send some information. Server handles the information
properly, again, no issue.
I quit telnet by using ^] and then writing quit. Breaking the connection
rather ungracefully.
The server properly recognises this isn't a clean disconnect and executes
the code to remove the socket.
I then get a range violation.
This is the main process and it's loop:
https://github.com/JGBrands/BlaatServer/blob/master/source/bserver.d
This is the server class, the code where it deletes the socket is at the
complete bottom in the function void destroySocket(int index);
https://github.com/JGBrands/BlaatServer/blob/master/source/server.d
Actually let me copy paste that. :-)
void destroySocket(int index) {
this.reads[index].close(); /* release resources. */
/* Remove the socket now. We don't want this around! It'll crash us! */
if (index != this.reads.length -1)
this.reads[index] = this.reads[this.reads.length -1];
this.reads = this.reads[0 .. this.reads.length -1];
writeln("Total connections: " ~ to!string(this.reads.length));
}
The code is primarily taken over from the listener.d example like I said, the
error I get is this:
core.exception.RangeError#server(61): Range violation
----------------
----------------
I'm lead to believe the function is deleting something it shouldn't, for those
interested, this is line 61 in server.d:
if (this.sset.isSet(this.reads[i])) {
Hopefully you guys can help me make more sense about this, am I missing something really obvious here?

Answer 1

As ratchet points out:
if (index != this.reads.length -1)
This does not verify that index is within range. It only validates that index is not the last element. This is fine as long as index has already been verified to be within range.
void destroySocket(int index)
in {
assert(index > -1);
assert(index < this.reads.length);
} body {
{