c++ - Trouble with packing / unpacking ints to and from char* -

I have the following code, which transfers four * for a receiver in an UDP socket: < Pre> structure packet {int seqNum; Int ackNum; Int payload size; Four * payload; }; -------------------------------------- // MTU = 1460 characters * payload = (four * Malloc (MTU); Int BitesCopyrid = Sprint (payload, "% d% d% d", dataty-> seconds.Secum, datat-> seconds.cnm, datat-> gt; secondsloadload); Cout & lt; & Lt; "Bytes copied:" & lt; & Lt; Bytespeed & lt; & Lt; Endl; // print 3 - will it print 12 (3 * sizeof (int))? Dome (payload, dataty-> second plywood); BytesSent = sendto (mySocket, Payload, Packet Size, 0, (Const Structured Socoders *) and Toonodes, Length);

The receiver looks like this:

  int n; Four buffer [MTU]; Berzo (buffer, MTU); Unsigned int length = sizeof (struct sockaddr_in); From the structure sockaddr_in; N = recvfrom (mySocket, buffer, MTU, 0, (Structure of Socadar *) and from, and Length); If (n & lt; 0) malfunction ("recvfrom"); Else {char * seqNum = (four *) malloc (sizeof (int)); Memcpy (seqNum, and buffer, sizeof (int)); Cout & lt; & Lt; "Segmentum:" & lt; & Lt; Seqnum & lt; & Lt; Endl; }   
 When I try to send 5 bytes of  payload :  105 #####  - Receiver output:  Sankanum: 105 # . When I send:  1010 ##########  (10 bytes of payload) receiver puts:  SeqNum: 1010 .  
  Note:   
 
 Running both boxes (Ubuntu VM)  
 About portability at all There is no need to worry, now   
  edit:   
 I have also tried to:  < Ex>  mempi (payload, and dataty-> sec.Secondum, size); Payload + = size (difference); Memcpy (payload, & amp; data is-> second.ackNum, sizeof (int)); Payload + = size (difference); Mempie (payload, & datite-> second payload size, size (intestine)); Payload + = size (difference); Dome (payload, dataty-> second plywood); Payload - = packet size; //sizeof (dataIt->.second.payload) + sizeof (int) + sizeof (int) + sizeof (int) bytescent = sendto (mySocket, payload, packet size, 0, (const struct sockaddr *) and toNode, length );   
 But this is wrong, because I am corrupting the stream while running it.   
 
 
 Again this code:  
  int bytescipid = sprint (payload, "% D% d% d", dataty-> seconds.Secum, dataty-> second.cnm, dataty-> second .payloadSize); Cout & lt; & Lt; "Bytes copied:" & lt; & Lt; Bytespeed & lt; & Lt; Endl;   
 I do not know why you were  bytes copied  12. There is nothing to do with  sizeof (int) ; The base can be converted into 10 digits using  Sprint ("% d" .) The length can be anywhere from  3  to  30  Or even if your  int  s is greater than 32-bit.  
 If you get the result  3 , then it indicates that all those integers This is not a very good data format, because the other end does not know how to unpack it. The receiver looks at  "12345" . Whether you sent  12   34   5 , or  1   23   45 ?  
 
  bytesSent = sendto (mySocket, payload, packet size, 0, (const struct sockaddr *) & amp; toNode, length);   
  length  and  packet sizes  are not defined anywhere.  
  Four * SecNum = (Four *) maulok (size); mempi (sikanum, and buffer, sizaf (int)); COAT & lt; & lt; "section:" & lieutenant; & Lt; To Qnum & lt; & Lt; Endl;   
 Passing a  char *  to  cout  in this way means that it expects a redundant string. However, (if there is actually a pack int in  buffer ), then you are sending it four bytes that do not make the string.  
 Is this code supposed to unpack the data you typed  sprintf ? Because if this is the case, then it is not that you are very mixed on the difference between  int , and represent the base 10 of that int.