diff --git a/lib/debug/server.rb b/lib/debug/server.rb
index 13a257d08..d08e6b788 100644
--- a/lib/debug/server.rb
+++ b/lib/debug/server.rb
@@ -15,8 +15,8 @@ def initialize
       @accept_m = Mutex.new
       @accept_cv = ConditionVariable.new
       @client_addr = nil
-      @q_msg = Queue.new
-      @q_ans = Queue.new
+      @q_msg = nil
+      @q_ans = nil
       @unsent_messages = []
       @width = 80
 
@@ -38,6 +38,9 @@ def initialize
               @sock.puts m
             }
             @unsent_messages.clear
+
+            @q_msg = Queue.new
+            @q_ans = Queue.new
           }
 
           setup_interrupt do
@@ -50,7 +53,9 @@ def initialize
           DEBUGGER__.message "Disconnected."
           @sock = nil
           @q_msg.close
+          @q_msg = nil
           @q_ans.close
+          @q_ans = nil
         end
       end
     end
@@ -83,9 +88,6 @@ def greeting
     end
 
     def process
-      @q_msg = Queue.new
-      @q_ans = Queue.new
-
       pause
 
       while line = @sock.gets
@@ -143,7 +145,15 @@ def sock skip: false
       if s = @sock         # already connection
         # ok
       elsif skip == true   # skip process
-        return yield nil
+        no_sock = true
+        r = @accept_m.synchronize do
+          if @sock
+            no_sock = false
+          else
+            yield nil
+          end
+        end
+        return r if no_sock
       else                 # wait for connection
         until s = @sock
           @accept_m.synchronize{
@@ -192,6 +202,7 @@ def puts str = nil
     def readline
       (sock do |s|
         s.puts "input"
+        sleep 0.01 until @q_msg
         @q_msg.pop
       end || 'continue').strip
     end
diff --git a/test/support/utils.rb b/test/support/utils.rb
index 5a211c29f..95808c7a3 100644
--- a/test/support/utils.rb
+++ b/test/support/utils.rb
@@ -60,16 +60,15 @@ def debug_on_local boot_options
 
     def debug_on_unix_domain_socket repl_prompt = '(rdbg:remote)'
       @mode = 'UNIX DOMAIN SOCKET'
-      boot_options = '-r debug/open'
       cmd = "#{__dir__}/../../exe/rdbg -A"
-      setup_remote_debuggee("#{RUBY} #{boot_options} #{temp_file_path}")
+      setup_remote_debuggee("#{__dir__}/../../exe/rdbg -O -- #{temp_file_path}")
       run_test_scenario(cmd, repl_prompt)
     end
 
     def debug_on_tcpip repl_prompt = '(rdbg:remote)'
       @mode = 'TCP/IP'
       cmd = "#{__dir__}/../../exe/rdbg -A #{RUBY_DEBUG_TEST_PORT}"
-      setup_remote_debuggee("#{__dir__}/../../exe/rdbg -O --port=#{RUBY_DEBUG_TEST_PORT} #{temp_file_path}")
+      setup_remote_debuggee("#{__dir__}/../../exe/rdbg -O --port=#{RUBY_DEBUG_TEST_PORT} -- #{temp_file_path}")
       run_test_scenario(cmd, repl_prompt)
     end
 
@@ -103,6 +102,7 @@ def run_test_scenario(cmd, repl_prompt)
                   write.puts(cmd)
                   cmd = @queue.pop
                 end
+
                 write.puts(cmd)
                 @last_backlog.clear
                 next # INTERNAL_INFO shouldn't be pushed into @backlog and @last_backlog