Show both serial and Wi-Fi working together

serial-and-wifi.ino

int last = 0;
char buf[256];

int toSerial(String s) {
  Serial.print("You said via REST API: ");
  Serial.println(s);

  memset(buf, 0, 256);
  int charsRead = 0;
  while (Serial.available() && charsRead < 255) {
    buf[charsRead] = Serial.read();
    charsRead++;
    delay(1);
  }

  if (0 < charsRead) {
    Serial.print("You said over serial: ");
    Serial.println(buf);
  } else {
    Serial.println("You haven't said anything over serial lately.");
  }

  return charsRead;
}

void setup() {
  Serial.begin(9600);
  Spark.function("to-serial", toSerial);
}

void loop() {
  if (millis() - last > 5000) {
    Serial.println("It's been 5 seconds.");
    last = millis();
  }
}