BUG

[puyangsky]

String c = sc.next().trim();
				if(c.equals("c")){
					//TODO: request access here!
					System.out.println("starting two phase commit.");
					coordinator.startCommit();
				}else if(c.equals("e")){
					System.out.println("exiting..");
					sc.close();
					lt.finish();
					return;
				}else if(c.equals("c")){
					System.out.println("Active clients:");
					for (Map.Entry<Socket, Participant> entry : connections.entrySet()) {
						System.out.println(entry.getValue());
					}
				}else{
					System.out.println("unrecognized command.");
				}

Here are two same if statements "c.equals("c")", which I think is a bug.

[lham]

Yeah, this looks wrong.

[yuno-gen]

while(true){
String c = sc.next().trim();
if(c.equals("c")){
//TODO: request access here!
System.out.println("starting two phase commit.");
coordinator.startCommit();
}else if(c.equals("e")){
System.out.println("exiting..");
sc.close();
lt.finish();
return;
}else if(c.equals("p")){
System.out.println("Active clients:");
for (Map.Entry<Socket, Participant> entry : connections.entrySet()) {
System.out.println(entry.getValue());
}
}else{
System.out.println("unrecognized command.");
}
}

you can always change one of the "c"s just like I did for checking the participants I made it to "p".
This should work.