Arduino, PC, Ethernet, and VB

Using Arduino Interfacing w/ Software on the Computer
3

Have you checked the Arduino server with a web browser? It seems you declare the server, but do not start it in setup.

void setup()
{
  pinMode(8,OUTPUT);
  Ethernet.begin(mac, local_ip);
  Serial.begin(9600);

  // start the server listening on port 80
  server.begin();
}

edit: I should have posted a link to the server sketch example in the playground (playground = wiki).
http://playground.arduino.cc/Code/WebServerST