can't connect to SITL - udp

[ygratz]

I try connecting to a SITL using takeoff_and_land example. I use udp to 127.0.0.1:14540

1. For some reason I get the following fault: MAVSDK version: v0.37.0 (mavsdk_impl.cpp:21) Trying Connection: udp://:14540 Waiting to discover system... [04:40:14|Info ] New system on: 127.0.0.1:45563 (with sysid: 1) (udp_connection.cpp:190) [04:40:14|Debug] New: System ID: 1 Comp ID: 1 (mavsdk_impl.cpp:418) [04:40:14|Debug] Component Autopilot (1) added. (system_impl.cpp:324) [04:40:15|Warn ] sending again after 0.507609 s, retries to do: 3 (520). (mavlink_commands.cpp:239) [04:40:15|Warn ] sending again after 1.01592 s, retries to do: 2 (520). (mavlink_commands.cpp:239) [04:40:16|Warn ] sending again after 1.51982 s, retries to do: 1 (520). (mavlink_commands.cpp:239) [04:40:16|Error] Retrying failed (520) (mavlink_commands.cpp:260) No autopilot found.

2. Where is mavlink_commands.cpp located?