您没有提到您使用什么 API 来接收数据包。不要将 IP 地址写入数据包本身,因为数据包在到达您之前可能会经过多次网络地址转换。
您可以使用常规 BSD 套接字来完成此任务。还有一些围绕 BSD 套接字的 Foundation 类,但我没有亲自使用它们,所以我不能给你一个像样的例子。
// for IPv4 (IPv6 is a little different)
ssize_t received;
char buffer[0x10000];
struct sockaddr_in listenAddr;
struct sockaddr_in fromAddr;
socklen_t fromAddrLen = sizeof fromAddr;
listenAddr.sin_family = AF_INET;
listenAddr.sin_port = htons(12345); // change to whatever port
listenAddr.sin_addr.s_addr = htonl(INADDR_ANY);
int s = socket(AF_INET, SOCK_DGRAM, 0); // create UDP socket
if (s == -1)
exit(1); // failed to create socket
if (bind(s, (struct sockaddr *) &listenAddr, sizeof listenAddr))
exit(2); // failed to bind to port 12345 for any address
received = recvfrom(s, buffer, sizeof buffer, 0, (struct sockaddr *)&fromAddr, &fromAddrLen);
if (received == -1)
exit(3); // some failure trying to receive data
// check the contents of buffer, the address of the source will be in
// fromAddr.sin_addr.s_addr but only if (fromAddrLen == sizeof fromAddr)
// after the call to recvfrom.
char display[16] = {0};
inet_ntop(AF_INET, &fromAddr.sin_addr.s_addr, display, sizeof display);
NSLog (@"The source is %s.", display);
// could show "The source is 201.19.91.102."