sendFilePayload method
Implementation
@override
void sendFilePayload(File file, String channel) {
//TODO: review the format
final bytes = file.readAsBytesSync();
var mime = lookupMimeType(file.path);
String base64Image = "data:" +
(mime ?? "text/plain") +
";base64," +
base64Encode(bytes) +
"," +
basename(file.path);
sendPayload(base64Image, channel);
}