Update README.MD

README.MD

@@ -7,4 +7,10 @@ To compile the proto files, you can do it both within IntelliJ as well as with t
 
 The command you need to launch is:
 
-mvn package
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+mvn package
+
+To launch a "main" from the command line:
+
+mvn package exec:java -Dexec.mainClass=chat.ChatServer
+
+(replace "chat.ChatServer" with the class containing a main method that you need to launch)
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