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尝试发送包含最多 30 个字符以及其他识别信息的数据包。这是构造函数。

packet::packet(int t, int s, int l, char * d){
type = t;
seqnum = s;
length = l;
data = d;
}

对于我的课程，我们需要通过以下方式进行序列化和反序列化：

void packet::serialize(char * spacket){
sprintf (spacket, "%d %d %d %s", type, seqnum, length, data);   
}

void packet::deserialize(char * spacket){
char * itr;
itr = strtok(spacket," ");
char * null_end;

this->type = strtol(itr, &null_end, 10);

itr = strtok(NULL, " ");
this->seqnum = strtol (itr, &null_end, 10);

itr = strtok(NULL, " ");
this->length = strtol (itr, &null_end, 10);

if(this->length == 0){
    data = NULL;
}
else{
    itr = strtok(NULL, " ");    
    for(int i=0; i < this->length; i++){ // copy data into char array
        this->data[i] = itr[i];
    }
  }
}

此客户端代码导致我的 server.exe 出现分段错误：

char sendPayload[512];
char receivePayload[512];
char sendBuffer[30] = {'1', '2', '3', '\0'};
int receivedPacketType = 0;
int sendPacket;
int receivePacket;

bzero(receivePayload, 512);
bzero(sendPayload, 512);

for (int iterator = 0; iterator < 8; iterator++)
{
    //Setting up sendPayload for sending.
    packet sendpckt(1, iterator, strlen(sendBuffer), sendBuffer);
    sendpckt.serialize((char*)sendPayload);

    //Datagram send to emulator.
    sendPacket = sendto(sendSocket, &sendPayload, sizeof(sendPayload), 0, (struct sockaddr *)&sendSocketStruct, sendSocketLen);

    //Datagram wait on receive from emulator.
    receivePacket = recvfrom(receiveSocket, &receivePayload, sizeof(sendPayload), 0, (struct sockaddr *)&receiveSocketStruct, &receiveSocketLen);

    //Setting up packet for receivePayload.
    packet recvpckt(0,0,0,NULL);
    recvpckt.deserialize((char*)receivePayload);
    recvpckt.printContents();

    bzero(receivePayload, 512);
    bzero(receivePayload, 512);

}

这是服务器端接收代码：

char receivePayload[512];
char sendPayload[512];
int expectedSeqNum = 0;
int receivedPacketType = 0;
int receivedPacketSeqNum = 0;
int receivedPacketLength = 0;
char receivedPacketData[512];
int receivePacket;
int sendPacket;
std:string finalText;

bzero(receivePayload, 512);
bzero(sendPayload, 512);

do
{
    receivePacket = recvfrom(receiveSocket, &receivePayload, sizeof(receivePayload), 0, (struct sockaddr *)&receiveSocketStruct, &receiveSocketLen);
    packet recvpckt(0, 0, 0, NULL);
    recvpckt.deserialize((char*)receivePayload);
    receivedPacketType = recvpckt.getType();
    receivedPacketSeqNum = recvpckt.getSeqNum();
    receivedPacketLength = recvpckt.getLength();
    bzero(receivePayload, 512);
    recvpckt.printContents();

    if (receivedPacketType == 3)
    {
        break;
    }

    /*
    if (receivedPacketType == 1)
    {
        *receivedPacketData = *recvpckt->getData();
        printf("%s\n", receivedPacketData);
    }
    */

    if (receivedPacketSeqNum == expectedSeqNum)
    {
        packet sendpckt(0, expectedSeqNum, 0, NULL);
        sendpckt.serialize((char*)sendPayload);
        sendPacket = sendto(sendSocket, &sendPayload, sizeof(sendPayload), 0, (struct sockaddr *)&sendSocketStruct, sendSocketLen);
        bzero(sendPayload, 512);
        expectedSeqNum = expectedSeqNum + 1;
        if (expectedSeqNum > 7)
        {
            expectedSeqNum = 0;
        }

    }
    else
    {
        packet sendpckt(0, expectedSeqNum, 0, NULL);
        sendpckt.serialize((char*)sendPayload);
        sendPacket = sendto(sendSocket, &sendPayload, sizeof(sendPayload), 0, (struct sockaddr *)&sendSocketStruct, sendSocketLen);
        bzero(sendPayload, 512);
    }

} while (1);

如果我将数据包中的数据内容清空并将长度设置为 0，则数据包传输得非常好。一旦我尝试增加数据包的长度并给它一个字符串，服务器就会遇到分段错误。

我在这里想念什么？我觉得我的缓冲区太大了，或者我错误地指向或引用了某些东西。

4

1 回答 1

1

你像这样初始化你的接收数据包（recvpckt）：

packet recvpckt(0, 0, 0, NULL);

这使得data成员为 NULL。

然后调用recvpckt.deserialize，它会写入未初始化的data数组。您需要在某处（例如 in recvpckt.deserialize）分配内存，或者将数组的地址传递给recvpckt构造函数以将数据写入其中。

这种问题最好使用调试器来解决。

于 2017-03-21T20:29:14.670 回答