Problem : Could not open Selected VM debug port (8700). Make sure you do not have another instance of DDMS or of the eclipse plugin running. If it's being used by something else, choose a new port number in the preferences.
Answer : 해당포트(8700)를 다른 곳에서 사용하고 있을때 생기는 문제.
Window -> Preferences -> Android -> DDMS - > Selected debug port 의 포트를
다른 포트번호로(ex 8601,8602..)변경해 주면 해결.