Have async raise 4xx/5xx status codes and add simultaneous connection limit
Have async raise 4xx/5xx status codes and add simultaneous connection limit

cmu-delphi/delphi-epidata,cmu-delphi/delphi-epidata,cmu-delphi/delphi-epidata,cmu-delphi/delphi-epidata,cmu-delphi/delphi-epidata,cmu-delphi/delphi-epidata