docs: add loginFail server inst

docs/protocol.tex

@@ -18,8 +18,8 @@ application for 'fake' trading assets, to practice investing. The document
 contains explainations on how to implement the papertrader application. It 
 should be noted that the document isn't `production-ready' until this sentence 
 is removed. The document will go over the roles of the master server, and the
-worker servers, how they interact with eachother and the communication protocol,
-and finally, suggestions on server side implementations.
+worker servers, how they interact with eachother and the communication 
+protocol, and finally, suggestions on server side implementations.
 
 \section{Overview}
 This section contains the required terminology and modelling of the PaperTrader
@@ -33,7 +33,8 @@ lockdown. Meaning, critical data should be kept secure.
 
 \subsubsection{Outer World}
 This is the frontend, including the desktop cleint, mobile client, or the
-website client. The data here is controlled by the authorization of the account.
+website client. The data here is controlled by the authorization of the 
+account.
 
 \subsubsection{Critical Data}
 Cirtical Data are all data types that shouldn't be tampered with without
@@ -791,4 +792,8 @@ on the sessionID, i.e if the sessionID is for username all data is returned. On
 success, the server would return teh data transfer mechanism. On failure, the
 server would return the `dataFill' instruction.
 
+\subsubsection{loginFail}
+This is a server return instruction. It means that a login has failed. The
+reason is in the arguments attached with the instruction.
+
 \end{document}