在iPhone上收回UDP數據包

Question

我試圖通過Wi-Fi在MAC OS和iPod之間建立UDP通信，此時我可以從iPod發送數據包，並且我可以看到這些數據包有權MAC和IP地址（我使用wireshark監視網絡），但MAC只在wireshark打開時接收數據包，否則recvfrom（）返回-1。

當我嘗試從MAC傳輸到iPhone我有相同的結果，我可以看到數據包發送，但iPhone似乎並沒有得到它們。

我用下面的代碼來發送：

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; 

這個代碼，即可獲得：

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's 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; 

我缺少什麼？

Answer 1

這將是很好的獲得關於您發送的數據的長度的更多信息。 我會假設你正試圖發送一個ASCII string。

而且，這似乎是要麼從來沒有所謂的或無限發送循環：

while (cond) 
    sntBytes += sendto(sockfd, message, strlen(message), 0, p->ai_addr, p->ai_addrlen); 

你可能想使用代碼，實際上包括了一些錯誤檢查：

發送字符串

int sendResult = send(connectedSocket, stringBuffer, stringLength, 0); 
    if (sendResult == -1) { 
     perror("Error while trying to send string!"); 
    } 
    else { 
     NSLog(@"String '%s' sent successfully", stringBuffer); 
    } 

接收字符串

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); 
    }