diff --git a/lab3/link_emulator.err b/lab3/link_emulator.err
new file mode 100644
index 0000000000000000000000000000000000000000..e69de29bb2d1d6434b8b29ae775ad8c2e48c5391
diff --git a/lab3/link_emulator.out b/lab3/link_emulator.out
new file mode 100644
index 0000000000000000000000000000000000000000..e69de29bb2d1d6434b8b29ae775ad8c2e48c5391
diff --git a/lab3/recv.c b/lab3/recv.c
index 84f3e99bfe2aa8d2f7399955da3d1cbb810a49d9..46915188f013bbd66b98c997e130be96bc132a82 100644
--- a/lab3/recv.c
+++ b/lab3/recv.c
@@ -23,28 +23,80 @@ int main(int argc,char** argv) {
init(HOST,PORT);
struct l3_msg t;
+
+ int output_file = open("recv.data", O_WRONLY | O_APPEND);
+
+ while (1)
+ {
+ /* Receive the frame from the link */
+ int len = link_recv(&t, sizeof(struct l3_msg));
+ DIE(len < 0, "Receive message");
- /* Receive the frame from the link */
- int len = link_recv(&t, sizeof(struct l3_msg));
- DIE(len < 0, "Receive message");
+ /* We have to convert it to host order */
+ uint32_t recv_sum = ntohl(t.hdr.sum);
+ t.hdr.sum = 0;
+ int sum_ok = (simple_csum((void *) &t, sizeof(struct l3_msg)) == recv_sum);
+ /* TODO 2: Change to crc32 */
- /* We have to convert it to host order */
- uint32_t recv_sum = ntohl(t.hdr.sum);
- t.hdr.sum = 0;
- int sum_ok = (simple_csum((void *) &t, sizeof(struct l3_msg)) == recv_sum);
- /* TODO 2: Change to crc32 */
+ /* Since we are sending messages with a payload of 1500 - sizeof(header), most of the times the bytes from
+ * 30 - 1500 will be corrupted and thus when we are printing or string message "Hello world" we see no probems.
+ * This will be visible when we will be sending a file */
- /* Since we are sending messages with a payload of 1500 - sizeof(header), most of the times the bytes from
- * 30 - 1500 will be corrupted and thus when we are printing or string message "Hello world" we see no probems.
- * This will be visible when we will be sending a file */
+ printf("[RECV] len=%d; sum(%s)=0x%04hx; payload=\"%s\";\n", t.hdr.len, sum_ok ? "GOOD" : "BAD", recv_sum, t.payload);
- printf("[RECV] len=%d; sum(%s)=0x%04hx; payload=\"%s\";\n", t.hdr.len, sum_ok ? "GOOD" : "BAD", recv_sum, t.payload);
+ /* TODO 3.1: In a loop, recv a frame and check if the CRC is good */
+ if (sum_ok == 0)
+ {
+ /* TODO 3.2: If the crc is bad, send a NACK frame */
+
+ printf("Frame is busted\n");
+
+ /* Look in common.h for the definition of l3_msg */
+ struct l3_msg nack;
- /* TODO 3.1: In a loop, recv a frame and check if the CRC is good */
+ /* We set the payload */
+ sprintf(nack.payload, "nnnnnnnn");
+ nack.hdr.len = strlen(nack.payload) + 1;
- /* TODO 3.2: If the crc is bad, send a NACK frame */
+ /* Add the checksum */
+ /* Note that we compute the checksum for both header and data. Thus
+ * we set the checksum equal to 0 when computing it */
+ nack.hdr.sum = 0;
+
+ /* Since sum is on 32 bits, we have to convert it to network order */
+ nack.hdr.sum = htonl(simple_csum((void *) &nack, sizeof(struct l3_msg)));
+
+ /* Send the message */
+ link_send(&nack, sizeof(struct l3_msg));
+
+ } else {
+ /* TODO 3.2: Otherwise, write the frame payload to a file recv.data */
+ printf("Good frame\n");
+
+
+ write(output_file, t.payload, strlen(t.payload));
+ /* Look in common.h for the definition of l3_msg */
+ struct l3_msg ack;
+
+ /* We set the payload */
+ sprintf(ack.payload, "aaaaaaaa");
+ ack.hdr.len = strlen(ack.payload) + 1;
+
+ /* Add the checksum */
+ /* Note that we compute the checksum for both header and data. Thus
+ * we set the checksum equal to 0 when computing it */
+ ack.hdr.sum = 0;
+
+ /* Since sum is on 32 bits, we have to convert it to network order */
+ ack.hdr.sum = htonl(simple_csum((void *) &ack, sizeof(struct l3_msg)));
+
+ /* Send the message */
+ link_send(&ack, sizeof(struct l3_msg));
+ break;
+ }
+ }
+
- /* TODO 3.2: Otherwise, write the frame payload to a file recv.data */
/* TODO 3.3: Adjust the corruption rate */
diff --git a/lab3/send.c b/lab3/send.c
index c9f4e5b203d9838cf1b06a7e09ff81187bded35a..cc5c43c6c752b28ac4775e6d798888712160f5db 100644
--- a/lab3/send.c
+++ b/lab3/send.c
@@ -20,29 +20,47 @@ int main(int argc,char** argv) {
/* Look in common.h for the definition of l3_msg */
struct l3_msg t;
- /* We set the payload */
- sprintf(t.payload, "Hello my World of PC!");
- t.hdr.len = strlen(t.payload) + 1;
+ while (1)
+ {
+ /* We set the payload */
+ sprintf(t.payload, "Hello my World of PC!");
+ t.hdr.len = strlen(t.payload) + 1;
- /* Add the checksum */
- /* Note that we compute the checksum for both header and data. Thus
- * we set the checksum equal to 0 when computing it */
- t.hdr.sum = 0;
+ /* Add the checksum */
+ /* Note that we compute the checksum for both header and data. Thus
+ * we set the checksum equal to 0 when computing it */
+ t.hdr.sum = 0;
- /* Since sum is on 32 bits, we have to convert it to network order */
- t.hdr.sum = htonl(simple_csum((void *) &t, sizeof(struct l3_msg)));
+ /* Since sum is on 32 bits, we have to convert it to network order */
+ t.hdr.sum = htonl(simple_csum((void *) &t, sizeof(struct l3_msg)));
- /* TODO 2.0: Call crc32 function */
+ /* TODO 2.0: Call crc32 function */
- /* Send the message */
- link_send(&t, sizeof(struct l3_msg));
+ /* Send the message */
- /* TODO 3.1: Receive the confirmation */
+ link_send(&t, sizeof(struct l3_msg));
- /* TODO 3.2: If we received a NACK, retransmit the previous frame */
+ /* TODO 3.1: Receive the confirmation */
+ struct l3_msg response;
+ int len_resp = link_recv(&response, sizeof(struct l3_msg));
+ DIE(len_resp < 0, "Receive message");
- /* TODO 3.3: Update this to read the content of a file and send it as
- * chunks of that file given a MTU of 1500 bytes */
+ /* We have to convert it to host order */
+ uint32_t recv_sum_resp = ntohl(response.hdr.sum);
+ response.hdr.sum = 0;
+ int sum_ok_resp = (simple_csum((void *) &response, sizeof(struct l3_msg)) == recv_sum_resp);
+ /* TODO 2: Change to crc32 */
+
+ /* TODO 3.2: If we received a NACK, retransmit the previous frame */
+ if (strchr(response.payload, 'n'))
+ {
+ link_send(&t, sizeof(struct l3_msg));
+ } else break;
+
+ /* TODO 3.3: Update this to read the content of a file and send it as
+ * chunks of that file given a MTU of 1500 bytes */
+ }
+
return 0;
}