void B_input(struct pkt packet)
{
//struct pkt new_packet_b;
int my_checksum=0;
B_transport++;
my_checksum=packet.seqnum+packet.acknum;
for(int i=0;i<20;i++)
my_checksum+=packet.payload[i];
memset(new_packet_b.payload,'\0',20);
if(expectedseqno==0)
{
new_packet_b.seqnum=-1;
new_packet_b.acknum=1;
new_packet_b.checksum=new_packet_b.acknum+new_packet_b.seqnum;
for(int i=0;i<20;i++)
new_packet_b.checksum+=new_packet_b.payload[i];
}
if((my_checksum==packet.checksum )&& (packet.seqnum ==expectedseqno))//reject out of order packets
{
tolayer5(1,packet.payload);
B_application++;
new_packet_b.acknum=1;
new_packet_b.seqnum=expectedseqno;
new_packet_b.checksum=new_packet_b.acknum+new_packet_b.seqnum;
for(int i=0;i<20;i++)
new_packet_b.checksum+=new_packet_b.payload[i];
tolayer3(1,new_packet_b);
expectedseqno++;
}
else
{
tolayer3(1,new_packet_b);//to tell sender which packet is needed
}
}
/*Sender State that handles acknowledgment*/
void A_Receiver_State(struct pkt packet)
{
bool corrupt = isPacketCorrupt(packet.checksum,packet.seqnum,packet.acknum,packet.payload);
int acknum = packet.acknum;
if(!corrupt)
{
base = acknum+1;
int endOfWindow = base +windowSize;
//send all packets from nextseq to end of new windowsize which are in buffer
while(nextSequenceNum<endOfWindow && nextSequenceNum<senderPacketCounter)
{
tolayer3(A,senderBuffer[nextSequenceNum]);
nextSequenceNum++;
}
if(base==nextSequenceNum) //All acknowledgements have been have been received
{
stoptimer(A);
}
//one ack have been received, thus send one packet from new window
else
{
stoptimer(A);
starttimer(A,timeout);
}
}
}
/*
* B_input(packet),where packet is a structure of type pkt. This routine
* will be called whenever a packet sent from the A-side (i.e., as a result
* of a tolayer3() being done by a A-side procedure) arrives at the B-side.
* packet is the (possibly corrupted) packet sent from the A-side.
*/
void B_input(struct pkt packet) {
struct pkt ack;
if (iscorrupt(packet)) {
return;
}
if (packet.acknum == DATAACK) {
if (!iscorrupt(packet) && packet.seqnum != Bexpectedseqnum) { //wrong seq num
ack = Bpastack;
tolayer3(BEntity,ack);
return;
}
if (!iscorrupt(packet) && packet.seqnum == Bexpectedseqnum) { //right seqnum
ack.checksum = 0;
ack.seqnum = packet.seqnum;
ack.acknum = ACK;
memcpy(ack.payload,packet.payload,MESSAGE_LENGTH);
ack.checksum = genchecksum(ack);
Bpastack = ack;
tolayer3(BEntity,ack);
struct msg message;
memcpy(message.data,packet.payload,MESSAGE_LENGTH);
tolayer5(BEntity,message);
Bexpectedseqnum++;
return;
}
}
////new stuff
if (packet.acknum == ACK) {
if (Bbase >= (packet.seqnum + 1)) {
if (packet.seqnum + 1 == Bnextseqnum) {
stopTimer(BEntity);
}
return;
}
Bbase = packet.seqnum + 1;
if (Bbase == Bnextseqnum) {
stopTimer(BEntity);
}
else {
stopTimer(BEntity);
startTimer(BEntity,TIMERAMT);
}
}
////old stuff
}
/*Initial state of receiver side*/
void B_Initial_State(struct pkt packet)
{
struct msg message;
createMessageforLayer5(&packet,&message);
bool corrupt = isPacketCorrupt(packet.checksum,packet.seqnum,packet.acknum,message.data);
int seqnum = packet.seqnum;
struct pkt datapacket; //creating packet containing acknowledgment
int checksum=0;
if(!corrupt && seqnum==expectedSeqNum)
{
int ack=expectedSeqNum; //send ack for received packet
createDataPacket(&datapacket,0,ack,checksum,"");
createCheckSum(&datapacket); //set checksum
datapacket.acknum = expectedSeqNum; //re assigning value for correctness
tolayer3(B,datapacket);
tolayer5(B,message.data);
int i;
for(i=0;i<20;i++)
{
printf("%c",message.data[i]);
}
printf("\n");
//printf("\nB SIDE : Printing Packet payload Sent Above %s\n",message.data);
//printf("\nB SIDE : Printing Acknum %d sent from B to A \n",datapacket.acknum);
//incrementing the expected sequence number
expectedSeqNum++;
}
else //send previous acknowledgment
{
int ack =expectedSeqNum-1;
createDataPacket(&datapacket,0,ack,checksum,"");
createCheckSum(&datapacket); //set checksum
datapacket.acknum = expectedSeqNum-1; //reassign for correctness
tolayer3(B,datapacket);
}
}
void send_nack(int caller, struct pkt *pkt_to_nack)
{
int seqnum = pkt_to_nack->seqnum;
char msg[MSGSIZE] = {'N','A','C','K',0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
struct pkt *nack_pkt = make_pkt(seqnum, msg);
nack_pkt->acknum = 0;
tolayer3(caller, *nack_pkt);
}
struct pkt send_packet(int target, int seq, int ack, char* payload)
{
struct pkt packet_out;
packet_out = make_packet(seq, ack, payload);
printf("%c: Sending packet (%d, %d, %d ,'%s')\n",(target == 0) ? 'A' : 'B' ,packet_out.seqnum, packet_out.acknum, packet_out.checksum, packet_out.payload);
stats.packets_sent++;
tolayer3(target, packet_out); //send out the built packet from A
return packet_out;
}
/*
* A_timerinterrupt() This routine will be called when A's timer expires
* (thus generating a timer interrupt). You'll probably want to use this
* routine to control the retransmission of packets. See starttimer()
* and stoptimer() in the writeup for how the timer is started and stopped.
*/
void A_timerinterrupt() {
int i;
for (i = Abase; i < (Anextseqnum - Abase - 1), i < (Abase + WINDOW_SIZE); i++) {
if (Aglobalarray[i] == NULL) {
//removed timer here
return;
}
tolayer3(AEntity, *Aglobalarray[i]);
}
startTimer(AEntity, TIMERAMT);
return;
}
/*Initial Sender State*/
void A_Initial_State()
{
//printf("before if loop nextseq %d, base+window %d\n",nextSequenceNum,(base+windowSize));
if(nextSequenceNum<(base+windowSize))
{
//printf("Entered if loop\n");
tolayer3(A,senderBuffer[nextSequenceNum]);
if(base==nextSequenceNum)
starttimer(A,timeout);
nextSequenceNum++;
}
}
/*Function sends packets in between the window base and (nextSeqNum-1)
* It is called during timeout of oldest unAcknowledged packet*/
void reSendAllIntermediatePackets()
{
int i;
int tempBase =base;
int msgCount = nextSequenceNum-base-1; //number of packets to be sent
//printf("msgcount value %d\n",msgCount);
for(i=0;i<msgCount;i++)
{
//printf("tempBase value %d\n",tempBase);
tolayer3(A,senderBuffer[tempBase]);
//printf("^^^^^^^^^^^^^^^^^^^^^ RESENT MESSAGES %s\n",senderBuffer[tempBase].payload);
tempBase++;
}
}
/*
* B_timerinterrupt() This routine will be called when B's timer expires
* (thus generating a timer interrupt). You'll probably want to use this
* routine to control the retransmission of packets. See starttimer()
* and stoptimer() in the writeup for how the timer is started and stopped.
*/
void B_timerinterrupt() {
////new stuff
int i;
for (i = Bbase; i < (Bnextseqnum - Bbase - 1), i < (Bbase + WINDOW_SIZE); i++) {
if (Bglobalarray[i] == NULL) {
//removed timer here
return;
}
tolayer3(BEntity, *Bglobalarray[i]);
}
startTimer(BEntity, TIMERAMT);
return;
////old stuff
}
/* called when A's timer goes off */
void A_timerinterrupt() //ram's comment - changed the return type to void.
{
//printf("\n in A_timerinterrupt.. Calling startimer");
starttimer(0,TIMEOUT);
timer_A_started=1;
int i;
for(i=base;i<nextseqnum;i++)// send packets in window
{
tolayer3(0,my_packet[i]);
A_transport++;
}
}
/*Initial state of receiver side*/
void B_Initial_State(struct pkt packet) {
struct msg message;
createMessageforLayer5(&packet, &message);
bool corrupt = isPacketCorrupt(packet.checksum, packet.seqnum,
packet.acknum, message.data);
int seqnum = packet.seqnum;
struct pkt datapacket; //creating packet containing acknowledgment
int checksum = 0;
if (!corrupt) {
//send ack for all packets lying under below range
if (seqnum >= (receiverBase - receiverWindowSize)
&& seqnum <= (receiverBase + receiverWindowSize - 1)) {
int ack = seqnum; //send ack for received packet
createDataPacket(&datapacket, 0, ack, checksum, "");
createCheckSum(&datapacket); //set checksum
datapacket.acknum = seqnum; //re assigning value for correctness
tolayer3(B, datapacket); //this is done irrespective of any action
//printf("\nB SIDE : Printing Acknum %d sent from B to A \n",
// datapacket.acknum);
B_StoreMessageInReceiverBuffer(seqnum, &message); //marks AckSent as true
}
//for values lying under current window
if (seqnum >= receiverBase
&& seqnum <= (receiverBase + receiverWindowSize - 1)) {
/* Handling data sent to layer5*/
int returnVal = returnNextMaximumContiguousSequenceAcknowledged(B);
if (returnVal != -1) {
sendMessagestoLayer5(returnVal);
}
}
} //Un_corrupt packet Loop Ends
}
/*Function sends packet with "Id" nextSeqNumber, Also add event to timer List*/
void A_sendPacket(int sequence) {
insertLinkedList(sequence, get_sim_time());
tolayer3(A, senderBuffer[sequence]);
//printf("Packet sent from A to B Sequence Number : %d \n",sequence);
if (nextSequenceNum == base) //whenever it starts fresh after receiving all Acks, start the timer
{
//printf("TIMER HAS BEEN STARTED at %f\n",get_sim_time());
//stoptimer(A);
starttimer(A, timeout);
}
}
/* called when A's timer goes off */
void A_timerinterrupt(void)
{
int i;
if (TRACE > 0)
printf("----A: time out,resend packets!\n");
for(i=0; i<windowcount; i++) {
if (TRACE > 0)
printf ("---A: resending packet %d\n", (buffer[(windowfirst+i) % WINDOWSIZE]).seqnum);
tolayer3(A,buffer[(windowfirst+i) % WINDOWSIZE]);
packets_resent++;
if (i==0) starttimer(A,RTT);
}
}
void A_output(struct msg message) {
Atemp = (struct pkt*) malloc(sizeof(struct pkt));
memcpy(Atemp->payload,message.data,MESSAGE_LENGTH);
Atemp->seqnum = Anextseqnum;
Atemp->acknum = DATAACK;
Atemp->checksum = 0;
Atemp->checksum = genchecksum(*Atemp);
Aglobalarray[Anextseqnum] = Atemp;
if (Anextseqnum < (Abase + WINDOW_SIZE)) { //(!getTimerStatus( AEntity )) { //will succeed if timer is off
tolayer3(AEntity,*Atemp);
if (Abase == Anextseqnum) {
startTimer(AEntity,TIMERAMT);
}
}
Anextseqnum++;
return;
}
/* called from layer 3, when a packet arrives for layer 4 at B*/
void B_input(struct pkt packet)
{
struct pkt sendpkt;
int i;
/* if not corrupted and received packet is in order */
if ( (!IsCorrupted(packet)) && (packet.seqnum == expectedseqnum) ) {
if (TRACE > 0)
printf("----B: packet %d is correctly received, send ACK!\n",packet.seqnum);
packets_received++;
/* deliver to receiving application */
tolayer5(B, packet.payload);
/* send an ACK for the received packet */
sendpkt.acknum = expectedseqnum;
/* update state variables */
expectedseqnum = (expectedseqnum + 1) % SEQSPACE;
}
else {
/* packet is corrupted or out of order resend last ACK */
if (TRACE > 0)
printf("----B: packet corrupted or not expected sequence number, resend ACK!\n");
if (expectedseqnum == 0)
sendpkt.acknum = SEQSPACE - 1;
else
sendpkt.acknum = expectedseqnum - 1;
}
/* create packet */
sendpkt.seqnum = B_nextseqnum;
B_nextseqnum = (B_nextseqnum + 1) % 2;
/* we don't have any data to send. fill payload with 0's */
for ( i=0; i<20 ; i++ )
sendpkt.payload[i] = '0';
/* computer checksum */
sendpkt.checksum = ComputeChecksum(sendpkt);
/* send out packet */
tolayer3 (B, sendpkt);
}
/* called from layer 5 (application layer), passed the message to be sent to other side */
void A_output(struct msg message)
{
struct pkt sendpkt;
int i;
/* if not blocked waiting on ACK */
if ( windowcount < WINDOWSIZE) {
if (TRACE > 1)
printf("----A: New message arrives, send window is not full, send new messge to layer3!\n");
/* create packet */
sendpkt.seqnum = A_nextseqnum;
sendpkt.acknum = NOTINUSE;
for ( i=0; i<20 ; i++ )
sendpkt.payload[i] = message.data[i];
sendpkt.checksum = ComputeChecksum(sendpkt);
/* put packet in window buffer */
/* windowlast will always be 0 for alternating bit; but not for GoBackN */
windowlast = (windowlast + 1) % WINDOWSIZE;
buffer[windowlast] = sendpkt;
windowcount++;
/* send out packet */
if (TRACE > 0)
printf("Sending packet %d to layer 3\n", sendpkt.seqnum);
tolayer3 (A, sendpkt);
/* start timer if first packet in window */
if (windowcount == 1)
starttimer(A,RTT);
/* get next sequence number, wrap back to 0 */
A_nextseqnum = (A_nextseqnum + 1) % SEQSPACE;
}
/* if blocked, window is full */
else {
if (TRACE > 0)
printf("----A: New message arrives, send window is full\n");
window_full++;
}
}
/* called from layer 5, passed the data to be sent to other side */
void A_output(struct msg message) //ram's comment - students can change the return type of the function from struct to pointers if necessary
{
//Buffer 1000 packets, used it to send when window moves ahead
if(SND_BUFSIZE<1000)
{
A_application++;
strncpy(buffer[SND_BUFSIZE].data, message.data,20);
SND_BUFSIZE++;
}
if(nextseqnum<(base+WINSIZE)){
struct pkt packet_a;
strncpy(packet_a.payload,buffer[nextseqnum].data,20);
packet_a.seqnum=nextseqnum;
packet_a.acknum=-1;//it is not acknowledgment
packet_a.checksum=packet_a.seqnum+packet_a.acknum;
for(int i=0;i<20;i++)
packet_a.checksum+=packet_a.payload[i];
my_packet[my_packet_no++]=packet_a;
tolayer3(0,packet_a);
A_transport++;
if(base==nextseqnum)
{
starttimer(0,TIMEOUT);
timer_A_started=1;
}
nextseqnum++;
}
}
/*
* Just like A_output, but residing on the B side. USED only when the
* implementation is bi-directional.
*/
void B_output(struct msg message) {
//////new stuff
Btemp = (struct pkt*) malloc(sizeof(struct pkt));
memcpy(Btemp->payload,message.data,MESSAGE_LENGTH);
Btemp->seqnum = Bnextseqnum;
Btemp->acknum = DATAACK;
Btemp->checksum = 0;
Btemp->checksum = genchecksum(*Btemp);
Bglobalarray[Bnextseqnum] = Btemp;
if (Bnextseqnum < (Bbase + WINDOW_SIZE)) { //(!getTimerStatus( AEntity )) { //will succeed if timer is off
tolayer3(BEntity,*Btemp);
if (Bbase == Bnextseqnum) {
startTimer(BEntity,TIMERAMT);
}
}
Bnextseqnum++;
return;
/////old stuff
}
/*
* B_input(packet),where packet is a structure of type pkt. This routine
* will be called whenever a packet sent from the A-side (i.e., as a result
* of a tolayer3() being done by a A-side procedure) arrives at the B-side.
* packet is the (possibly corrupted) packet sent from the A-side.
*/
void B_input(struct pkt packet) {
struct msg message; // Store message retrived from network
struct pkt ack; // Store ack packet
// Pass message to layer 5 when it not corrupted and when it has expected seqnum
if (not_corrupted(packet) && (packet.seqnum == rev_seqnum)) {
strncpy(message.data, packet.payload, MESSAGE_LENGTH);
tolayer5(BEntity, message);
// Make ack message
ack = prepare_pkt(1, rev_seqnum, NULL);
// flip expected sequence number of packet
rev_seqnum = !rev_seqnum;
} else {
// Make ack message
ack = prepare_pkt(1, !rev_seqnum, NULL);
}
// Send ack message
tolayer3(BEntity, ack);
}
void send_pkt(int caller, struct pkt *pkt_to_send)
{
tolayer3(caller, *pkt_to_send);
starttimer(caller, TIMEOUT);
}
/* called from layer 3, when a packet arrives for layer 4 */
void A_input(struct pkt packet)
{
/*printf("\nIn a_input");
printf("\n Packet details- seqnum %d acknum %d checksum %d payload %s \n", packet.seqnum,
packet.acknum, packet.checksum, packet.payload);*/
int my_checksum=packet.seqnum+packet.acknum;
for(int i=0;i<20;i++)
my_checksum+=packet.payload[i];
//if ((my_checksum==packet.checksum))
if ((my_checksum==packet.checksum) )
{
if(base != (packet.seqnum+1))
{
base=packet.seqnum+1;//move window ahead
if(base==nextseqnum)
{
if(timer_A_started==1)
{
stoptimer(0);
timer_A_started=0;
}
}
else
{
if(timer_A_started==1)
{
stoptimer(0);
timer_A_started=0;
}
starttimer(0,TIMEOUT);
timer_A_started=1;
}
}
//transmit all buffered packets if are in window
int buf_index=base;
while((nextseqnum<(base+WINSIZE)) && (nextseqnum< SND_BUFSIZE)){
printf("\n**********Sending packet in A_input");
struct pkt packet_a;
strncpy(packet_a.payload,buffer[nextseqnum].data,20);
packet_a.seqnum=nextseqnum;
packet_a.acknum=-1;//it is not acknowledgment
packet_a.checksum=packet_a.seqnum+packet_a.acknum;
for(int i=0;i<20;i++)
packet_a.checksum+=packet_a.payload[i];
my_packet[my_packet_no++]=packet_a;
tolayer3(0,packet_a);
A_transport++;
if(base==nextseqnum)
{
//printf("\nCalling startimer");
starttimer(0,TIMEOUT);
timer_A_started=1;
}
nextseqnum++;
}
}
}