好吧，如果你看一下我的一些以前的问题，我一直在努力得到一个简单的连接起来，以C插座运行（我仍然相当新的程序的整个网络的因素，但每个人都有开始的地方， 对？）。 我在下面列出的是我到目前为止，当我执行它，我没有得到任何错误的代码，但在同一时间，我没有得到另一端的数据包。 顺便说一句，我在Objective-C编程多播套接字和“msgStatus”只是在我的GUI标签（它正确地迷上了，所以没有问题存在）。 我只是没有看到我要去哪里错了。 可能有人可能会帮助我，或点我在正确的方向？ 谢谢！
#define MAX_LEN 1024 /* maximum string size to send */
#define MIN_PORT 1024 /* minimum port allowed */
#define MAX_PORT 65535 /* maximum port allowed */
#define MYPORT 5673 /* port we will be using for our multicast socket */
-(void)broadcastMessage {//(NSString*)msg {
NSLog(@"broadcastMessage - Stage 1");
NSString *msg = @"From Master";
mc_ttl = 3; // number of node hops the message is allowed to travel across the network
// define the port we will be using
mc_port = MYPORT;
/* create a socket for sending to the multicast address */
if ((sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) {
NSLog(@"ERROR: broadcastMessage - socket() failed");
return;
}
mc_addr.sin_family = AF_INET;
mc_addr.sin_addr.s_addr = inet_addr("225.0.0.37");
mc_addr.sin_port = htons(mc_port);
if (bind(sock, (struct sockaddr *) &mc_addr, sizeof(struct sockaddr_in)) < 0) {
NSLog(@"ERROR: bind not successful");
return;
}
NSLog(@"broadcastMessage - Stage 2");
/* set the TTL (time to live/hop count) for the send */
if ((setsockopt(sock, IPPROTO_IP, IP_MULTICAST_TTL, (void*) &mc_ttl, sizeof(mc_ttl))) < 0) {
NSLog(@"ERROR: broadcastMessage - setsockopt() failed");
return;
}
NSLog(@"broadcastMessage - Stage 3");
/* construct a multicast address structure - erase everything in the structure first*/
memset(&mc_addr, 0, sizeof(mc_addr));
// prepare the message to be sent
char send_str[MAX_LEN];
/* clear send buffer */
memset(send_str, 0, sizeof(send_str));
// convert the message to a C string to send
[msg getCString:send_str maxLength:MAX_LEN encoding:NSASCIIStringEncoding];
//while (fgets(send_str, MAX_LEN, stdin)) {
NSLog(@"broadcastMessage - Stage 4");
// send_len = strlen(send_str);
/* send string to multicast address */
if ((sendto(sock, send_str, sizeof(send_str), 0, (struct sockaddr *) &mc_addr, sizeof(mc_addr))) != sizeof(send_str)) {
NSLog(@"ERROR: broadcastMessage - sendto() sent incorrect number of bytes");
return;
}
NSLog(@"broadcastMessage - Stage 5");
/* clear send buffer */
memset(send_str, 0, sizeof(send_str));
NSLog(@"broadcastMessage - Stage 6");
close(sock);
}
-(void)listenForPackets {
listeningFlag_on = 1;
NSLog(@"listenForPackets - Stage 1");
if ((listeningSock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) {
NSLog(@"ERROR: listenForPackets - socket() failed");
return; // make the method return an int instead of void and use this statement to check for errors
}
// set reuse port to on to allow multiple binds per host
if ((setsockopt(listeningSock, SOL_SOCKET, SO_REUSEADDR, &listeningFlag_on, sizeof(listeningFlag_on))) < 0) {
NSLog(@"ERROR: listenForPackets - setsockopt() failed");
return; // make the method return an int instead of void and use this statement to check for errors
}
NSLog(@"listenForPackets - Stage 2");
// construct a multicast address structure after erasing anything in the listeningmc_addr structure
memset(&listeningmc_addr, 0, sizeof(listeningmc_addr));
listeningmc_addr.sin_family = AF_INET;
listeningmc_addr.sin_addr.s_addr = htonl(INADDR_ANY);
listeningmc_addr.sin_port = htons(mc_port);
// bind multicast address to socket
if ((bind(listeningSock, (struct sockaddr *) &listeningmc_addr, sizeof(listeningmc_addr))) < 0) {
NSLog(@"ERROR: listenForPackets - bind() failed");
return; // make the method return an int instead of void and use this statement to check for errors
}
//******************************************************************************************************************************
//******************************************************************************************************************************
NSString *ipAddress = [[NSString alloc] initWithString:self.getIPAddress];
const char *tmp = [ipAddress UTF8String];
listeningMc_addr_str = tmp;
printf("%s\n", listeningMc_addr_str);
listeningMc_req.imr_multiaddr.s_addr = inet_addr("225.0.0.37");
listeningMc_req.imr_interface.s_addr = htonl(INADDR_ANY);
// send an ADD MEMBERSHIP message via setsockopt
if ((setsockopt(listeningSock, IPPROTO_IP, IP_ADD_MEMBERSHIP, (void*) &listeningMc_req, sizeof(listeningMc_req))) < 0) {
NSLog(@"ERROR: listenForPackets - setsockopt() failed");
int err = errno;
NSLog(@"errno - %i", err);
NSLog(@"Error = %s", strerror(err));
perror("ERROR");
return; // make the method return an int instead of void and use this statement to check for errors
}
NSLog(@"listenForPackets - Stage 3");
for (;;) { // loop forever
// clear the receive buffers & structs
memset(listeningRecv_str, 0, sizeof(listeningRecv_str));
listeningFrom_len = sizeof(listeningFrom_addr);
memset(&listeningFrom_addr, 0, listeningFrom_len);
// block waiting to receive a packet
if ((listeningRecv_len = recvfrom(listeningSock, listeningRecv_str, MAX_LEN, 0, (struct sockaddr*)&listeningFrom_addr, &listeningFrom_len)) < 0) {
NSLog(@"ERROR: listenForPackets - recvfrom() failed");
return; // make the method return an int instead of void and use this statement to check for errors
}
NSLog(@"listenForPackets - Stage 4");
NSString *tmpy = [[NSString alloc] initWithCString:listeningRecv_str encoding:NSASCIIStringEncoding];
msgStatus.text = tmpy;
NSLog(@"ERROR");
}
// received string
printf("Received %d bytes from %s: ", listeningRecv_len, inet_ntoa(listeningFrom_addr.sin_addr));
printf("%s", listeningRecv_str);
}
// send a DROP MEMBERSHIP message via setsockopt
if ((setsockopt(listeningSock, IPPROTO_IP, IP_DROP_MEMBERSHIP, (void*) &listeningMc_req, sizeof(listeningMc_req))) < 0) {
NSLog(@"ERROR: listenForPackets - setsockopt() failed");
//return 1; // make the method return an int instead of void and use this statement to check for errors
}
close(listeningSock);
NSLog(@"listenForPackets - Stage 5 - Complete");
}
下面是我使用提取我的IP地址的代码。
-(NSString *)getIPAddress {
NSString *address = @"error";
struct ifaddrs *interfaces; // = NULL;
struct ifaddrs *temp_addr; // = NULL;
int success = 0;
// retrieve the current interfaces - returns 0 on success
success = getifaddrs(&interfaces);
if (success == 0)
{
// Loop through linked list of interfaces
temp_addr = interfaces;
while(temp_addr != NULL)
{
if(temp_addr->ifa_addr->sa_family == AF_INET)
{
// Check if interface is en0 which is the wifi connection on the iPhone
if([[NSString stringWithUTF8String:temp_addr->ifa_name] isEqualToString:@"en0"])
{
// Get NSString from C String
address = [NSString stringWithUTF8String:inet_ntoa(((struct sockaddr_in *)temp_addr->ifa_addr)->sin_addr)];
}
}
temp_addr = temp_addr->ifa_next;
}
}
// Free memory
freeifaddrs(interfaces);
return address;
}
