You asked for plain text. If that is not what you want, then remove it.
client.println("HTTP/1.1 200 OK");
// remove the next line
client.println("Content-Type: text/plain");
client.println();
You asked for plain text. If that is not what you want, then remove it.
client.println("HTTP/1.1 200 OK");
// remove the next line
client.println("Content-Type: text/plain");
client.println();