implement semaphore for SendBiMessage

During async applications, when multiple SendBiMessage requests are
made while one is not completely resolved, KRPC hangs or errors.
This change makes sure that the exchange is complete before accepting new one.

src/KRPC.jl

@@ -32,6 +32,14 @@ mutable struct KRPCConnection
     one_to_many::Dict{UInt64, Array{UUID, 1}}
     listeners::Dict{UUID, Listener}
     active::Channel
+    semaphore::Base.Semaphore
+
+    function KRPCConnection(conn::TCPSocket, stream_conn::TCPSocket, identifier::Array{UInt8, 1}, active::Channel)
+        new(
+            conn, stream_conn, identifier,
+            Nothing(), Dict{UInt8, Array{UUID, 1}}(), Dict{UUID, Listener}(), active, Base.Semaphore(1)
+        )
+    end
 end
 
 function Base.show(io::IO, conn::KRPCConnection) 

src/connection.jl

@@ -78,7 +78,7 @@ function kerbal_connect(client_name::String, host::String="localhost", port::Int
     connect_or_error(str_conn, krpc.schema.ConnectionRequest(client_identifier=resp.client_identifier,_type=krpc.schema.ConnectionRequest_Type.STREAM))
 
     active = Channel(0)
-    conn = KRPCConnection(conn, str_conn, resp.client_identifier, Nothing(), Dict{UInt8, Array{UUID, 1}}(), Dict{UUID, Listener}(), active)
+    conn = KRPCConnection(conn, str_conn, resp.client_identifier, active)
     conn.str_listener = @async stream_listener(conn)
     bind(active, conn.str_listener)
 

src/raw.jl

@@ -28,13 +28,15 @@ function RecvRawProto(inp::IO)
 end
 
 function SendBiMessage(conn::KRPCConnection, req::KRPC.krpc.schema.Request)
+    Base.acquire(conn.semaphore)
     iob = PipeBuffer()
     SendRawProto(conn.conn, req)
     res = readproto(RecvRawProto(conn.conn), krpc.schema.Response())
 
     if hasproperty(res, :error)
         throw(make_error(res.error))
     end
+    Base.release(conn.semaphore)
     return res
 end