Windows Server 2012 R2 machines not communicating on AWS:EC2

Executive Summary:

Primary Goal The goal is to have WCF communication between Windows Machines using UDP broadcast.

Secondary Goal Under the 'Network' to be able to see the other computers.

Current Topography:

Machines:

- Machine A: Windows Server 2012 RC2
- Machine B: Windows Server 2012 RC2
- Machine C: Ubuntu used as an FTP server\Static web server for publishing code\installing apps

Subnet:

- Subnet A: 172.xx.xx.0/20  (used as the private network)

Firewalls:

- Machine A: Private Network = OFF; Public Network = ON
- Machine B: Private Network = OFF; Public Network = ON

Security Groups:

- Security Group A:
  - All TCP ports open: 0-65535 to any machine on Subnet A
  - All UDP ports open: 0-65535 to any machine on Subnet A
  - All ICMP open to any machine on Subnet A

Current Communication:

From Machine A:

- Using CMD: ping <Machine B> gets a response
- Using CMD: ping <Machine C> gets a response
- Using Server Manager: Can add/communicate and see running services on Machine B
- Using NMap to Machine B:  Host down (doesn't work)
- Using NMap to Google DNS (8.8.8.8):  works perfectly fine
- Using NMap to Machine C: host down (doesn't work)
- Using FTP to Machine C: works perfect
- Using http to get to Machine C: works perfect

From Machine B:

- Using CMD: ping <Machine A> gets a response
- Using CMD: ping <Machine C> gets a response
- Using Server Manager: Can add/communicate and see running services on Machine A
- Using NMap to Machine A:  Host down (doesn't work)
- Using NMap to Google DNS (8.8.8.8):  works perfectly fine
- Using NMap to Machine C: host down (doesn't work)
- Using FTP to Machine C: work perfect
- Using http to get to Machine C: works perfect

From Machine C:

- ping <Machine A> get a response (works)
- ping <Machine B> gets a response (works)
- NMap (intensive scan + UDP ) to Machine A&B:

Host is up.
1961 Closed ports, 27 open|filtered ports
PORTS     STATE   SERVICE        VERSION
135/tcp   open    msrpc          MSFT Windows RPC
139/tcp   open    netbios-ssn  
445/tcp   open    netbios-ssn
3389/tcp  open    ms-wbt-server  MSFT Terminal Service
49152/tcp open    ms-wbt-server  MSFT Windows RPC
49153/tcp open    ms-wbt-server  MSFT Windows RPC
49154/tcp open    ms-wbt-server  MSFT Windows RPC 
49155/tcp open    ms-wbt-server  MSFT Windows RPC
49157/tcp open    ms-wbt-server  MSFT Windows RPC
49158/tcp open    ms-wbt-server  MSFT Windows RPC
49160/tcp open    ms-wbt-server  MSFT Windows RPC
137/udp   open    ms-wbt-server  MSFT Windows NT netbios-ssn (workgroup: WORKGROUP)

I am at a complete loss at this point.