user7402: I'm using this simple code
#include <Bridge.h>
#include <YunServer.h>
#include <YunClient.h>

YunServer server;

void setup() {
  Serial.begin(9600);
  Bridge.begin();
  server.listenOnLocalhost();
  server.begin();
}

void loop() {
  YunClient client = server.accept();
  if (client) {
    Serial.println("client");
    process(client);
    client.stop();
   } else {
     Serial.println("no client");
   }
   delay(50); 
}

void process(YunClient client) {
  String command = client.readStringUntil('/');
  Serial.println(command);
  if (command == "turnLeft") {
    Serial.println("Gira a sinistra");
  }
  if (command == "turnRight") {
    Serial.println("Gira a destra");
  }
  if (command == "goTo") {
    String value = client.readStringUntil('/goTo/');
    Serial.println(value);
  }
}

but it seems to have problem with bridge (or server, or client, i cannot understand) because it only write "no client" on the serial.
I can not understand what is wrong. 

user7904: Probably too late to answer your question. Your problem is on line 
if (client) 

Change it to 
if(client.connected())

which actually returns true when client is connected. 

7402: <p>I'm using this simple code</p>

<pre><code>#include &lt;Bridge.h&gt;
#include &lt;YunServer.h&gt;
#include &lt;YunClient.h&gt;

YunServer server;

void setup() {
  Serial.begin(9600);
  Bridge.begin();
  server.listenOnLocalhost();
  server.begin();
}

void loop() {
  YunClient client = server.accept();
  if (client) {
    Serial.println("client");
    process(client);
    client.stop();
   } else {
     Serial.println("no client");
   }
   delay(50); 
}

void process(YunClient client) {
  String command = client.readStringUntil('/');
  Serial.println(command);
  if (command == "turnLeft") {
    Serial.println("Gira a sinistra");
  }
  if (command == "turnRight") {
    Serial.println("Gira a destra");
  }
  if (command == "goTo") {
    String value = client.readStringUntil('/goTo/');
    Serial.println(value);
  }
}
</code></pre>

<p>but it seems to have problem with bridge (or server, or client, i cannot understand) because it only write "no client" on the serial.</p>

<p>I can not understand what is wrong. </p>
 7904: <p>Probably too late to answer your question. Your problem is on line </p>

<pre><code>if (client) 
</code></pre>

<p>Change it to </p>

<pre><code>if(client.connected())
</code></pre>

<p>which actually returns true when client is connected. </p>
