PDUTransmit.c

#include "safeUtil.h"
#include <string.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <errno.h>
#include "PDUTransmit.h"

#define MAXBUF 1024


//create PDU, send PDU, return data bytes sent
int sendPDU(int socketNumber, uint8_t* dataBuffer, int lengthOfData){
    uint16_t h_newLen=lengthOfData+2;
    uint8_t udpDataBuffer[h_newLen];

    uint16_t nw_newLen = htons(h_newLen);
    memcpy(udpDataBuffer,&nw_newLen,2);
    memcpy(udpDataBuffer+2,dataBuffer,lengthOfData);

    return safeSend(socketNumber, udpDataBuffer, h_newLen, 0);  

}

int sendPDUWithFlag(int clientSocket, uint8_t flag, uint8_t* dataBuffer, int lengthOfData) {
    uint16_t h_newLen=lengthOfData+3;
    uint8_t udpDataBuffer[h_newLen];

    // length at offset 0
    uint16_t nw_newLen = htons(h_newLen);
    memcpy(udpDataBuffer, &nw_newLen, 2);           
    //
    // flag at offset 2
    udpDataBuffer[2] = flag;                       
    memcpy(udpDataBuffer + 3, dataBuffer, lengthOfData);  // data starts at offset 3
    //

    return safeSend(clientSocket, udpDataBuffer, h_newLen, 0);
}

int sendResponseFlag(int clientSocket, uint8_t flag){
    return sendPDU(clientSocket, &flag, 1);    //only send the flag
}

//returns the length of the message, excluding the 2 byte PDU
int recvPDU(int clientSocket, uint8_t* dataBuffer, int bufferSize){
    uint16_t PDULen=safeRecv(clientSocket, dataBuffer, 2, MSG_WAITALL);
    if(PDULen<0){
        return PDULen;  //catch errors
    }
    if(PDULen==0){
        return 0;
    }
    if(PDULen<2){
        return -1;  //this should not be possible, interpet it as an error
    }

    //aquire length of message from header
    uint16_t nw_recBytes=0;
    memcpy(&nw_recBytes,dataBuffer, 2);
    uint16_t h_recBytes=ntohs(nw_recBytes)-2;
    //

    if(h_recBytes<=0){
        return h_recBytes;  //return iether 0 (connection closed), or -1 (error)
    }
    if(h_recBytes>bufferSize){
        perror("MSG TO BIG");
        return -1;
    }

    //repeat the process, but listen for full message now
    h_recBytes= safeRecv(clientSocket, dataBuffer+2, h_recBytes, MSG_WAITALL);
    return h_recBytes;  //returns 0 for connection closed, -1 (error), or numBytes received on success
}