Use a solver address instead of a client address for a json-log filename

comm/server/main.py

@@ -162,7 +162,7 @@ def post():
     if not os.path.isdir(save_path):
         os.makedirs(save_path)
 
-    file_name = "{}-{}.json".format(receive_time_str, _client.replace(":", "."))
+    file_name = "{}-{}.json".format(receive_time_str, _solver.replace(":", "."))
     save_file_path = "{}/{}".format(save_path, file_name)
     with open(save_file_path, "w") as fp:
         json.dump(dat, fp, indent=4)