Ethernet shield can't connect server with keep alive connection

Using Arduino Networking, Protocols, and Devices
1

I want to use Ethernet shield to send/get data from my Apche server (localhost).

Ethernet(or Esp8266) ======(request.php by post method)==>>> server
Ethernet(or Esp8266) <<<=====(respond header and data)==== server

i send header to server to get data.

In my header:
If i use connection: close. This way seems ok.
But when i use connection: keep-alive. it can't connect or get any data till connection time out.
This is my header and way to send my data to server:

String result="";
   if (client.connect(server, 80)) {
    Serial.println("connected");
    // Make a HTTP request:
    client.println("POST myweb/getss.php HTTP/1.0");
    client.println("Host: localhost");
    client.println("Accept: *" "/" "*");
    client.println("Content-Length: " + String(data.length()));
    client.println("Content-Type: application/x-www-form-urlencoded");
    client.println("Connection: keep-alive");
    client.println();
    client.print(data);


  }
  else {
    // kf you didn't get a connection to the server:
    Serial.println("connection failed");
  }

And disconnect:

if (!client.connected()) {
    Serial.println();
    Serial.println("disconnecting.");
    client.flush();
    client.stop();
  }

Please tell me what problems?