连接客户端，获取连接到服务器的客户端的数据，连接一直保持直到连接的客户端超出范围。你可以使用client.stop()关闭它。

server.available()

None

客户端对象，如果没有客户端有数据需要读取，这个对象会关闭。

#include <Ethernet.h>
#include <SPI.h>
 
// the media access control (ethernet hardware) address for the shield:
byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };  
//the IP address for the shield:
byte ip[] = { 10, 0, 0, 177 };    
// the router's gateway address:
byte gateway[] = { 10, 0, 0, 1 };
// the subnet:
byte subnet[] = { 255, 255, 0, 0 };
 
 
// telnet defaults to port 23
EthernetServer server = EthernetServer(23);
 
void setup()
{
  // initialize the ethernet device
  Ethernet.begin(mac, ip, gateway, subnet);
 
  // start listening for clients
  server.begin();
}
 
void loop()
{
  // if an incoming client connects, there will be bytes available to read:
  EthernetClient client = server.available();
  if (client) {
    // read bytes from the incoming client and write them back
    // to any clients connected to the server:
    server.write(client.read());
  }
}