ESP8266 GET REPLY ERROR 501
Your problem lies in these lines:

esp8266.println("AT+CIPSEND=0,75");
esp8266.println("GET /f/pw9e1acqx7yb0gl.txt HTTP/1.1\r\n");
esp8266.println("Host:www.homeautomationserver.com\r\n\r\n");


You are mistakenly using println() instead of print() when sending the data. That imposes its own &lt;CR&gt;&lt;LF&gt; sequence on the end of the lines, yet you are adding the &lt;CR&gt;&lt;LF&gt; manually.  You are also incorrectly specifying 75 characters to send, so the result of all that is:

GET /f/pw9e1acqx7yb0gl.txt HTTP/1.1\r\n              37
\r\n                                                  2
Host:www.homeautomationserver.com\r\n                35
\r                                                    1
                                                   ----
                                                     75


I.e., your request is garbled. You need to change the println() to print() for the data printing and make sure the character count is correct:

esp8266.println("AT+CIPSEND=0,74");
esp8266.print("GET /f/pw9e1acqx7yb0gl.txt HTTP/1.1\r\n");
esp8266.print("Host:www.homeautomationserver.com\r\n\r\n");

GET /f/pw9e1acqx7yb0gl.txt HTTP/1.1\r\n              37
Host:www.homeautomationserver.com\r\n                35
\r\n                                                  2
                                                   ----
                                                     74


You should also include more detail and commands in your headers. Things like the length of the body (0 bytes) and the fact that the connection should be closed, and there really should be a space after the colon on the Host: header:

esp8266.println("AT+CIPSEND=0,113");
esp8266.print("GET /f/pw9e1acqx7yb0gl.txt HTTP/1.1\r\n");
esp8266.print("Connection: close\r\n");
esp8266.print("Content-Length: 0\r\n");
esp8266.print("Host: www.homeautomationserver.com\r\n\r\n");

GET /f/pw9e1acqx7yb0gl.txt HTTP/1.1\r\n              37
Connection: close\r\n                                19
Content-Length: 0\r\n                                19
Host: www.homeautomationserver.com\r\n               36
\r\n                                                  2
                                                  -----
                                                    113