I'd be surprised if this is doing what it looks like you expect:
client.println(postData.length() + "\r\n\r\n");
try:
client.print(postData.length() ) ;
client.println( "\r\n\r\n") ;
The documentation for the length() method of the String class is not detailed enough to use to determine what the return type is, but I guess it is not a String.