Hi,

I am relatively new to embedded ethernet. I have gone through the LWIP documentation and read about UDP and TCP basics from Jan Axelson's Ethernet Complete book. I still would like to know, how the UDP is implemented in the UDP socket example. I could understand setting up the Ethernet Interface of Mbed with EthernetNetif. What is the function of HOST , and how does the UDPsocket event function work. I read about multicast, and broadcast conn, however, it would be nice, if someone could explain it with reference to the below program.

00001 #include "mbed.h"
00002 #include "EthernetNetIf.h"
00003 #include "UDPSocket.h"
00004 EthernetNetIf eth;
00005 UDPSocket     cfgSocket;
00006 
00007 void onUDPSocketEvent(UDPSocketEvent e) {
00008     if ( e == UDPSOCKET_READABLE ) {
00009         char buf[64] = {0};
00010         Host host;
00011         while ( int len = cfgSocket.recvfrom( buf, 63, &host ) ) {
00012             if ( len <= 0 )
00013                 break;
00014             printf("From %d.%d.%d.%d: %s\n", host.getIp()[0], host.getIp()[1], host.getIp()[2], host.getIp()[3], buf);
00015         }
00016     }
00017 }
00018 
00019 int main() {
00020 //   pc.baud(115200);
00021     printf ("HEllo World - 7 *\n");
00022 
00023     EthernetErr ethErr = eth.setup();
00024     if ( ethErr == ETH_OK ) {
00025         IpAddr ip = eth.getIp();
00026         printf("mbed IP Address is %d.%d.%d.%d\r\n", ip[0], ip[1], ip[2], ip[3]);
00027     } else printf ("ETHERNETSETUP FAILED\n");
00028 
00029     printf("seting event\n");
00030     cfgSocket.setOnEvent(&onUDPSocketEvent);
00031     printf("seting host\n");
00032     Host x(IpAddr(),5555);
00033     printf("seting bind\n");
00034 
00035     UDPSocketErr udpErr = cfgSocket.bind( x );
00036     if ( udpErr != UDPSOCKET_OK )
00037         printf("error %d\n", udpErr);
00038 
00039     int i = 0;
00040     Host brdHost(IpAddr(255,255,255,255), 5555);                    //broadcast test msg
00041     char cfgRqstMsg[]="SERVER CONFIG REQUEST";
00042 
00043     Timer tmr;
00044     tmr.start();
00045     while (1) {
00046         Net::poll();
00047         if ( tmr.read() > 5) {
00048             tmr.reset();
00049             int nSent = cfgSocket.sendto(cfgRqstMsg,strlen(cfgRqstMsg),&brdHost);
00050             printf("PLONKER %d :: %d\n",++i,nSent);
00051             if ( nSent < 0 )
00052                 printf("error %d\n", (UDPSocketErr)nSent);
00053         }
00054     }
00055 }

can anyone help me with this ?

You can look at the sources of the NTPCLient (included in the NetServices library) to get a hint about how to use the UDP socket. But basically:

• the HOST is the server you want to send UDP packets to
• you get one event for each UDP packet you receive back

Hi Hendrik, I figured out about the host and events. I have been trying to create a TCP server now.