Yi Cameras - curl commands works but not netcat

[jcconnell]

I'm getting the following output from Netcat on the Yi camera:

# echo -ne $head | nc -i 5 local-hass-ip 8123
HTTP/1.0 400 Bad Request
Content-Type: application/json
Content-Length: 41
Date: Sun, 12 May 2019 22:50:12 GMT
Server: Python/3.6 aiohttp/3.5.4

{"message": "Data should be valid JSON."}#

This curl command works from my Mac:
curl --trace-ascii - -0 var=val -X POST -H "x-ha-access: password-example" -H "Content-Type: application/json" -d '{"payload": "{\"camera\":\"living room\",\"date\":\"02-16-2018\",\"time\":\"20:13\"}", "topic": "homeassistant/motion", "qos": 0, "retain": 0}' https://example/api/services/mqtt/publish

I'm executing these commands on the Yi from a telnet session:

body='{"payload": "{"camera":"living room","date":"02/26/18","time":"2:00pm"}", "topic": "homeassistant-motion", "qos": 0, "retain": 0}'
body_len=$(echo -n "$body" | wc -c)
head="POST /api/services/mqtt/publish HTTP/1.0\r\nHost: example.com\r\nUser-Agent: curl/7.47.0\r\nAccept: */*\r\nx-ha-access: example-password\r\nContent-Type: application/json\r\nContent-Length: ${body_len}\r\n\r\n${body}"
echo -ne $head | nc -i 5 local-hass-ip 8123

Any idea what the issue might be?