Unable to read text file from server

You are not waiting for the server to respond in this section of your code.

    if (client.available())  {
     char c = client.read();
      Serial.print(c);
    }
    else {
     Serial.println();
     Serial.println("disconnecting.");
     client.stop();
    }

Use this instead. This is the "Perfect World" version, but it should work ok as long as the connection doesn't break or the server doesn't stall.

while (client.connected()) {
  while(client.available()) {
    char ch = client.read();
    Serial.print(ch);
  }
}
client.stop();