Minecraft Server Resouce Pack won't download to client - java.net.MalformedURLException: no protocol

I'm running a Minecraft server on a local host in my house (FreeNas with MineOS plugin). I've configured my server.properties file with this line

server.properties

resource-pack="https://www.dropbox.com/s/4nbkkrfmxkw6n82/DefaultHDv1_7.zip?dl=1"

When I hit that link from any browser, the file downloads. I place the link into my server.properties file and restart the server. It gets the proper \ (escape) treatment:

server.properties

resource-pack="https://www.dropbox.com/s/4nbkkrfmxkw6n82/DefaultHDv1_7.zip?dl\=1"

And when I connect to the server, I'm asked if I would like to download the resource pack. Well, yes I would! Click yes, and I see

Downloading Texture Pack

Making request... 0%

This is when I manually tested my download links from my in-house data connection and on my 4gLTE provider, both worked fine so Dropbox is sending the file when requested. Kept the MC launcher running so I could read console output and found this.

[22:04:14] [File Downloader #5/INFO] [STDERR]: [java.lang.Throwable$WrappedPrintStream:println:748]: java.net.MalformedURLException: no protocol: "https://www.dropbox.com/s/4nbkkrfmxkw6n82/DefaultHDv1_7.zip?dl=1" [21:46:36] [File Downloader #3/INFO] [STDERR]: [java.lang.Throwable$WrappedPrintStream:println:748]: at java.net.URL.(URL.java:586) [21:46:36] [File Downloader #3/INFO] [STDERR]: [java.lang.Throwable$WrappedPrintStream:println:748]: at java.net.URL.(URL.java:483) [21:46:36] [File Downloader #3/INFO] [STDERR]: [java.lang.Throwable$WrappedPrintStream:println:748]: at java.net.URL.(URL.java:432) [21:46:36] [File Downloader #3/INFO] [STDERR]: [java.lang.Throwable$WrappedPrintStream:println:748]: at net.minecraft.util.HttpUtil$1.run(SourceFile:108) [21:46:36] [File Downloader #3/INFO] [STDERR]: [java.lang.Throwable$WrappedPrintStream:println:748]: at java.lang.Thread.run(Thread.java:745)

I've tried making the URL an HTTP link instead of HTTPS (in the thought that 'no protocol' meant my local Java client couldn't hit an HTTPS URL for one or another reason) . This also allows download via browser, but still will not download via the Minecraft client.

Using this:

server.properties

resource-pack="http://www.dropbox.com/s/4nbkkrfmxkw6n82/DefaultHDv1_7.zip?dl=1"

The URL then gets transformed to this (the standard escape characters are added):

server.properties

resource-pack="http://www.dropbox.com/s/4nbkkrfmxkw6n82/DefaultHDv1_7.zip?dl\=1"

But still I get the same 'no protocol' message in all my MC client outputs. We're running MC 1.7.10, both client systems have Java 1.8 (jre-8u66) installed, and work absolutely great with the exception of this one bug.

Do I need to downgrade to 1.6 for this to function properly? I can't upgrade my MC version to 1.8+ as the mods we run in our game don't apply properly.

I've worked around it for now by just using a local respack, but I'd prefer to just get this working the way it should (and the way I want it to :-) )

Any help out there?