@Override
	protected String toDSL() {
		return String.format("http --port=%d", port);
	}
Ensure that the source is ready to take requests by sending http header requests for up to the timeout specified
in millisecionds, sleeping 100 ms between attempts.

@param timeoutInMillis
@return a new SimpleHttpSource
@throws IllegalStateException if can't connect to the source within the given timeout.
spring-xd-test-fixtures/src/main/java/org/springframework/xd/test/fixtures/SimpleHttpSource.java