我正在尝试与我安装的服务器程序进行通信。服务器以构造的数据包的形式发送和接收所有数据,这些数据包遵循以下设置: int int int string nullbyte 像这样:
little endian signed int - > ID的大小(4个字节)+类型的大小(4个字节)+ Body的大小(空终止符的最小值为1)+空字节的最小值为10;
little endian signed int - > ID
little endian signed int - >包类型
Null终止ascii字符串 - >体
null byte
我设法读取数据包就好了但是当我尝试使用密码发送数据包时,服务器完全忽略它,这意味着数据包是错误的。我像这样构建数据包:
void Packet::build(){
/*
* Create unsigned char vector to store
* the data while we build the byte array
* and create a pointer so the byte array can
* be modified by the required functions.
*/
std::vector<unsigned char> packet(m_size);
unsigned char *ptr = packet.data();
/*
* Convert each of the three integers as well
* as the string into bytes which will be stored
* back into the memory that ptr points to.
*
* Packet data follows format:
* int32 -> Size of ID + Server Data + body (minimum of 10).
* int32 -> ID of request. Used to match to response.
* int32 -> Server Data type. Identifies type of request.
* String -> Minimum of 1 byte for null terminator.
* String -> Null terminator.
*/
storeInt32Le(ptr, m_sizeInPacket);
storeInt32Le(ptr, m_requestID);
storeInt32Le(ptr, m_serverData);
storeStringNt(ptr, m_body);
/*
* Store the vector in member variable m_cmdBytes;
*
*/
m_cmdBytes = packet;
}
storeInt32Le:
void Packet::storeInt32Le(unsigned char* &buffer, int32_t value) {
/*
* Copy the integer to a byte array using
* bitwise AND with mask to ensure the right
* bits are copied to each segment then
* increment the pointer by 4 for the next
* iteration.
*/
buffer[0] = value & 0xFF;
buffer[1] = (value >> 8) & 0xFF;
buffer[2] = (value >> 16) & 0xFF;
buffer[3] = (value >> 24) & 0xFF;
buffer += 4;
}
storeStringNt:
void Packet::storeStringNt(unsigned char* &buffer, const string &s) {
/*
* Get the size of the string to be copied
* then do a memcpy of string char array to
* the buffer.
*/
size_t size = s.size() + 1;
memcpy(buffer, s.c_str(), size);
buffer += size;
}
最后,我发送它:
bool Connection::sendCmd(Packet packet) {
unsigned char *pBytes = packet.bytes().data();
size_t size = packet.size();
while (size > 0){
int val = send(m_socket, pBytes, size, 0);
if (val <= 0) {
return false;
}
pBytes += val;
size -= val;
}
return true;
}
Packet :: bytes()只返回m_cmdBytes
答案 0 :(得分:0)
如评论中所述,您是:
对编译器int
数据类型的字节大小和字节序进行假设。由于您的协议需要非常特定的字节大小和endian作为整数,因此您需要在准备数据包时强制您的代码遵循这些要求。
错误地使用memcpy()
。您已将源缓冲区和目标缓冲区反转。
无法确保send()
实际上正确发送完整数据包。
尝试更像这样的事情:
void store_uint32_le(unsigned char* &buffer, uint32_t value)
{
buffer[0] = value & 0xFF;
buffer[1] = (value >> 8) & 0xFF;
buffer[2] = (value >> 16) & 0xFF;
buffer[3] = (value >> 24) & 0xFF;
buffer += 4;
}
void store_string_nt(unsigned char* &buffer, const std::string &s)
{
size_t size = s.size() + 1;
memcpy(buffer, s.c_str(), size);
buffer += size;
}
...
std::vector<unsigned char> packet(13 + m_body.size());
unsigned char *ptr = packet.data(); // or = &packet[0] prior to C++11
store_uint32_le(ptr, packet.size() - 4);
store_uint32_le(ptr, m_requestID);
store_uint32_le(ptr, m_serverData);
store_string_nt(ptr, m_body);
...
unsigned char *pBytes = packet.data(); // or = &packet[0] prior to C++11
size_t size = packet.size();
while (size > 0)
{
int val = send(m_socket, pBytes, size, 0);
if (val < 0)
{
// if your socket is non-blocking, enable this...
/*
#ifdef _WINDOWS // check your compiler for specific defines...
if (WSAGetLastError() == WSAEWOULDBLOCK)
#else
if ((errno == EAGAIN) || (errno == EWOULDBLOCK) || (errno == EINTR))
#endif
continue;
*/
return false;
}
if (val == 0)
return false;
pBytes += val;
size -= val;
}
return true;