Don't accept a keepalive interval of 0 seconds.

server/src/main/java/org/briarproject/snooze/SnoozeServer.java

@@ -58,7 +58,7 @@ public class SnoozeServer implements Runnable {
 				socket.setSoTimeout(SOCKET_TIMEOUT_MS);
 				DataInputStream in = new DataInputStream(socket.getInputStream());
 				OutputStream out = socket.getOutputStream();
-				int keepaliveIntervalSecs = in.readUnsignedShort();
+				int keepaliveIntervalSecs = Math.max(1, in.readUnsignedShort());
 				while (!socket.isClosed()) {
 					System.out.println("Writing: " + socket.getRemoteSocketAddress());
 					out.write(0);