Client can now connect to servers interactively

luprex/cpp/core/printbuffer.hpp

@@ -104,6 +104,8 @@ public:
     int last_line() const;
     
     // Get the current first unchecked line.
+    // "Unchecked" lines are lines in a non-authoritative model
+    // that haven't been verified through difference transmission.
     // Guaranteed to be between first_line and last_line inclusive.
     int first_unchecked() const;