UDP可靠的数据服务实现 [英] UDP reliable data service implementation

问题描述

我正在尝试使用UDP实现简单的数据传输.校验和有问题，给定包含数据的数据包，我应该如何实现校验和?还知道如何实现超时，以便触发重传吗?谢谢

I'm trying to implement a simple data transfer using UDP. I have a problem for the checksum, given a packet containing the data, how should I implement the checksum? also any idea how to implement the timeouts so it will trigger the retransmission ? Thanks

推荐答案

here's one approach for the internet checksum

unsigned short checkSum() {
    unsigned long sum = 0;
    int i;
    for(i=0; i < your packet length ; i++) {
        sum += (your packet data[i] & 0xFFFF);
    }
    while (sum >> 16) {
        sum = (sum & 0xFFFF) + (sum >> 16);
    }
    sum = ~sum;     
    return ((unsigned short) sum);
}

for the retransmission, you can set alarm to trigger timeout 
when packet is loss. you can do something using
signal (SIGALRM, timeout function);

Hope it helps!

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