Receiving UDP packets on iPhone
I am trying to establish UDP communication between MAC OS and iPod over Wi-Fi, at the moment I can send packets from the iPod and I can see that these packets have correct MAC addresses and IP addresses (I am using wireshark to monitor the network) , but the MAC only receives packets when wireshark is activated, otherwise recvfrom () returns -1.
When I try to transfer from MAC to iPhone, I have the same result, I can see that packets are being sent but the iPhone doesn't seem to receive them.
I am using the following code to send:
struct addrinfo hints;
int rv;
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_DGRAM;
if ((rv = getaddrinfo(IP, SERVERPORT, &hints, &servinfo)) != 0) {
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
return 1;
}
// loop through all the results and make a socket
for(p = servinfo; p != NULL; p = p->ai_next) {
if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) {
perror("talker: socket");
continue;
}
break;
}
if (p == NULL) {
fprintf(stderr, "talker: failed to bind socket\n");
return 2;
}
while (cond)
sntBytes += sendto(sockfd, message, strlen(message), 0, p->ai_addr, p->ai_addrlen);
return 0;
and this code to get:
struct addrinfo hints, *p;
int rv;
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC; // set
hints.ai_socktype = SOCK_DGRAM;
hints.ai_flags = AI_PASSIVE; // use to AF_INET to force IPv4 my IP
if ((rv = getaddrinfo(NULL, MYPORT, &hints, &servinfo)) != 0) {
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
return 1;
}
// loop through all the results and bind to the first we can
for(p = servinfo; p != NULL; p = p->ai_next) {
if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) {
perror("listener: socket");
continue;
}
if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
close(sockfd);
perror("listener: bind");
continue;
}
break;
}
if (p == NULL) {
fprintf(stderr, "listener: failed to bind socket\n");
return 2;
}
addr_len = sizeof their_addr;
fcntl(sockfd, F_SETFL,O_NONBLOCK);
int rcvbuf_size = 128 * 1024; // That 128Kb of buffer space.
setsockopt(sockfd, SOL_SOCKET, SO_RCVBUF,
&rcvbuf_size, sizeof(rcvbuf_size));
printf("listener: waiting to recvfrom...\n");
while (cond)
rcvBytes = recvfrom(sockfd, buf, MAXBUFLEN-1 , 0, (struct sockaddr *)&their_addr, &addr_len);
return 0;
What am I missing?
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It would be nice to have more information about the length of the data being sent. Let's say you are trying to send ASCII string
.
Also, this appears to be never called or an infinite dispatch loop:
while (cond)
sntBytes += sendto(sockfd, message, strlen(message), 0, p->ai_addr, p->ai_addrlen);
You might want to use code that actually includes some error checking:
Send string
int sendResult = send( connectedSocket, stringBuffer, stringLength, 0 );
if (sendResult == -1) {
perror("Error while trying to send string!");
}
else {
NSLog(@"String '%s' sent successfully", stringBuffer );
}
Get string
memset( ReceiveBuffer, '\0', sizeof(ReceiveBuffer) );
int receiveResult = recv( connectedSocket, ReceiveBuffer, sizeof(ReceiveBuffer), 0);
if ( receiveResult == -1 ) {
perror("recv");
}
else {
NSLog(@"String received successfully: '%s'", ReceiveBuffer );
}
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