{"action":"created","issue":{"url":"https://api.github.com/repos/esp8266/Arduino/issues/1802","repository_url":"https://api.github.com/repos/esp8266/Arduino","labels_url":"https://api.github.com/repos/esp8266/Arduino/issues/1802/labels{/name}","comments_url":"https://api.github.com/repos/esp8266/Arduino/issues/1802/comments","events_url":"https://api.github.com/repos/esp8266/Arduino/issues/1802/events","html_url":"https://github.com/esp8266/Arduino/issues/1802","id":142388240,"number":1802,"title":"UDP will not send until it has received at least one packet","user":{"login":"jgrina","id":5010218,"avatar_url":"https://avatars.githubusercontent.com/u/5010218?v=3","gravatar_id":"","url":"https://api.github.com/users/jgrina","html_url":"https://github.com/jgrina","followers_url":"https://api.github.com/users/jgrina/followers","following_url":"https://api.github.com/users/jgrina/following{/other_user}","gists_url":"https://api.github.com/users/jgrina/gists{/gist_id}","starred_url":"https://api.github.com/users/jgrina/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/jgrina/subscriptions","organizations_url":"https://api.github.com/users/jgrina/orgs","repos_url":"https://api.github.com/users/jgrina/repos","events_url":"https://api.github.com/users/jgrina/events{/privacy}","received_events_url":"https://api.github.com/users/jgrina/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":1,"created_at":"2016-03-21T15:43:56Z","updated_at":"2016-03-21T16:10:49Z","closed_at":null,"body":"\r\n### Basic Infos\r\n\r\n#### Hardware\r\nHardware:\t\t\tAdafruit Huzzah, NodeMCU, Adafruit Feather\r\nCore Version:      \t2.1\r\n\r\n### Description\r\n\r\nWhy does udp sendPacket wait for a received packet before sending? It is only the first send command that waits. If I force a transmit from host, a burst of \"sent\" packets appears and everything works great from there. Sends and receives go. I'm using Arduino IDE version 1.6.8 on a Win 7 machine for this listing, but the same happened with version 1.6.5 on my Win 10 machine. The ESP is an Adafruit Huzzah breakout board, but I also tried the ESP feather 8266 and the NodeMCU boards with the same result. I have updated the libraries to the latest code while installing IDE version 1.6.8.\r\n\r\nThe attached zipfiles are the program, monitor activity from the host and Arduino com port monitor\r\n\r\nThe arduino side file shows the ESP messages which have the sends, but no response until the host sends \"!Start\" message. The host side shows no messages until after the !Start message, then a burst of messages with responses to each message.\r\n\r\nI've tried several WiFi.modes, plus udp.flush(), udp.stop(), commands, but nothing changes.\r\n\r\nWith a looping program, this is not a major problem, I can use the monitor send function to start the ESP8266 noodes, but I want to use battery power and deep sleep function for some nodes. Deep sleep erases any knowledge of previous packet receives, so it must receive a packet every time it wakes up.\r\n\r\nHost side is Win 7, MegunoLink Pro\r\nI am using the Timer function in MegunoLink to broadcast a \"!Start\" message every 1/2 second\r\n\r\nJim\r\n\r\n### Settings in IDE\r\n\r\nModule:  \t\t\tHuzzah, generic ESP, NodeMCU 1.0\r\nFlash Size: \t\t4Mb\r\nCPU Frequency:\t\t80mhz\r\nFlash Mode:\t\t\tDIO\r\nFlash Frequency:\t40Mhz\r\nUpload Using:\t\tserial \r\nReset Method:\t\tck\r\n\r\n[zipfiles.zip](https://github.com/esp8266/Arduino/files/182561/zipfiles.zip)\r\n\r\n\r\n\r\n\r\n"},"comment":{"url":"https://api.github.com/repos/esp8266/Arduino/issues/comments/199360164","html_url":"https://github.com/esp8266/Arduino/issues/1802#issuecomment-199360164","issue_url":"https://api.github.com/repos/esp8266/Arduino/issues/1802","id":199360164,"user":{"login":"igrr","id":4349050,"avatar_url":"https://avatars.githubusercontent.com/u/4349050?v=3","gravatar_id":"","url":"https://api.github.com/users/igrr","html_url":"https://github.com/igrr","followers_url":"https://api.github.com/users/igrr/followers","following_url":"https://api.github.com/users/igrr/following{/other_user}","gists_url":"https://api.github.com/users/igrr/gists{/gist_id}","starred_url":"https://api.github.com/users/igrr/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/igrr/subscriptions","organizations_url":"https://api.github.com/users/igrr/orgs","repos_url":"https://api.github.com/users/igrr/repos","events_url":"https://api.github.com/users/igrr/events{/privacy}","received_events_url":"https://api.github.com/users/igrr/received_events","type":"User","site_admin":false},"created_at":"2016-03-21T16:10:49Z","updated_at":"2016-03-21T16:10:49Z","body":"It would be really helpful if you could post the sketch which may be used to reproduce this issue!"}}