diff --git a/platformio/commands/home/rpc/handlers/piocore.py b/platformio/commands/home/rpc/handlers/piocore.py
index 62dfdd3e..d4cc170f 100644
--- a/platformio/commands/home/rpc/handlers/piocore.py
+++ b/platformio/commands/home/rpc/handlers/piocore.py
@@ -33,42 +33,42 @@ except ImportError:
 
 class ThreadSafeStdBuffer(object):
 
-    def __init__(self, parent_stream, parent_thread_id):
-        self.parent_stream = parent_stream
-        self.parent_thread_id = parent_thread_id
-        self._buffer = {}
+    def __init__(self, parent_stream):
+        self._buffers = {thread_get_ident(): parent_stream}
+
+    def __getattr__(self, name):
+        thread_id = thread_get_ident()
+        if thread_id not in self._buffers:
+            raise AttributeError(name)
+        return getattr(self._buffers[thread_id], name)
 
     def write(self, value):
         thread_id = thread_get_ident()
-        if thread_id == self.parent_thread_id:
-            return self.parent_stream.write(
-                value if isinstance(value, string_types) else value.decode())
-        if thread_id not in self._buffer:
-            self._buffer[thread_id] = BytesIO()
-        return self._buffer[thread_id].write(value)
+        if thread_id not in self._buffers:
+            self._buffers[thread_id] = BytesIO()
+        try:
+            return self._buffers[thread_id].write(value)
+        except TypeError:
+            return self._buffers[thread_id].write(value.encode())
 
-    def flush(self):
-        return (self.parent_stream.flush()
-                if thread_get_ident() == self.parent_thread_id else None)
-
-    def getvalue_and_close(self, thread_id=None):
-        thread_id = thread_id or thread_get_ident()
-        if thread_id not in self._buffer:
-            return ""
-        result = self._buffer.get(thread_id).getvalue()
-        self._buffer.get(thread_id).close()
-        del self._buffer[thread_id]
+    def get_value_and_close(self):
+        thread_id = thread_get_ident()
+        result = ""
+        try:
+            result = self.getvalue()
+            self.close()
+            if thread_id in self._buffers:
+                del self._buffers[thread_id]
+        except AttributeError:
+            pass
         return result
 
 
 class PIOCoreRPC(object):
 
     def __init__(self):
-        cur_thread_id = thread_get_ident()
-        PIOCoreRPC.thread_stdout = ThreadSafeStdBuffer(sys.stdout,
-                                                       cur_thread_id)
-        PIOCoreRPC.thread_stderr = ThreadSafeStdBuffer(sys.stderr,
-                                                       cur_thread_id)
+        PIOCoreRPC.thread_stdout = ThreadSafeStdBuffer(sys.stdout)
+        PIOCoreRPC.thread_stderr = ThreadSafeStdBuffer(sys.stderr)
         sys.stdout = PIOCoreRPC.thread_stdout
         sys.stderr = PIOCoreRPC.thread_stderr
 
@@ -86,8 +86,8 @@ class PIOCoreRPC(object):
         def _call_cli():
             with util.cd((options or {}).get("cwd") or os.getcwd()):
                 exit_code = __main__.main(["-c"] + args)
-            return (PIOCoreRPC.thread_stdout.getvalue_and_close(),
-                    PIOCoreRPC.thread_stderr.getvalue_and_close(), exit_code)
+            return (PIOCoreRPC.thread_stdout.get_value_and_close(),
+                    PIOCoreRPC.thread_stderr.get_value_and_close(), exit_code)
 
         d = threads.deferToThread(_call_cli)
         d.addCallback(PIOCoreRPC._call_callback, "--json-output" in args)