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agent.c
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agent.c
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/* NOTE: 本程式僅供檢驗格式，並未檢查 congestion control 與 go back N */
/* NOTE: UDP socket is connectionless，每次傳送訊息都要指定ip與埠口 */
/* HINT: 建議使用 sys/socket.h 中的 bind, sendto, recvfrom */
/*
* 連線規範：
* 本次作業之 agent, sender, receiver 都會綁定(bind)一個 UDP socket 於各自的埠口，用來接收訊息。
* agent接收訊息時，以發信的位址與埠口來辨認訊息來自sender還是receiver，同學們則無需作此判斷，因為所有訊息必定來自agent。
* 發送訊息時，sender & receiver 必需預先知道 agent 的位址與埠口，然後用先前綁定之 socket 傳訊給 agent 即可。
* (如 agent.c 第126行)
*/
#include <stdio.h>
#include <time.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <string.h>
typedef struct {
int length;
int seqNumber;
int ackNumber;
int fin;
int syn;
int ack;
} header;
typedef struct{
header head;
char data[5000];
} segment;
void setIP(char *dst, char *src){
if(strcmp(src, "0.0.0.0") == 0 || strcmp(src, "local") == 0 || strcmp(src, "localhost")){
sscanf("127.0.0.1", "%s", dst);
}
else{
sscanf(src, "%s", dst);
}
return;
}
int main(int argc, char* argv[]){
int agentsocket, portNum, nBytes;
float loss_rate;
segment s_tmp;
struct sockaddr_in sender, agent, receiver, tmp_addr;
socklen_t sender_size, recv_size, tmp_size;
char ip[3][50];
int port[3], i;
if(argc != 7){
fprintf(stderr,"Usage: %s <sender IP> <recv IP> <sender port> <agent port> <recv port> <loss_rate>\n", argv[0]);
fprintf(stderr, "Example: ./agent local local 8887 8888 8889 0.3\n");
exit(1);
}
else{
setIP(ip[0], argv[1]);
setIP(ip[1], "local");
setIP(ip[2], argv[2]);
sscanf(argv[3], "%d", &port[0]);
sscanf(argv[4], "%d", &port[1]);
sscanf(argv[5], "%d", &port[2]);
sscanf(argv[6], "%f", &loss_rate);
}
/* Create UDP socket */
agentsocket = socket(PF_INET, SOCK_DGRAM, 0);
/* Configure settings in sender struct */
sender.sin_family = AF_INET;
sender.sin_port = htons(port[0]);
sender.sin_addr.s_addr = inet_addr(ip[0]);
memset(sender.sin_zero, '\0', sizeof(sender.sin_zero));
/* Configure settings in agent struct */
agent.sin_family = AF_INET;
agent.sin_port = htons(port[1]);
agent.sin_addr.s_addr = inet_addr(ip[1]);
memset(agent.sin_zero, '\0', sizeof(agent.sin_zero));
/* bind socket */
bind(agentsocket,(struct sockaddr *)&agent,sizeof(agent));
/* Configure settings in receiver struct */
receiver.sin_family = AF_INET;
receiver.sin_port = htons(port[2]);
receiver.sin_addr.s_addr = inet_addr(ip[2]);
memset(receiver.sin_zero, '\0', sizeof(receiver.sin_zero));
/* Initialize size variable to be used later on */
sender_size = sizeof(sender);
recv_size = sizeof(receiver);
tmp_size = sizeof(tmp_addr);
printf("可以開始測囉^Q^\n");
printf("sender info: ip = %s port = %d and receiver info: ip = %s port = %d\n",ip[0], port[0], ip[2], port[2]);
printf("agent info: ip = %s port = %d\n", ip[1], port[1]);
int total_data = 0;
int drop_data = 0;
int segment_size, index;
char ipfrom[1000];
char *ptr;
int portfrom;
srand(time(NULL));
while(1){
/* Receive message from receiver and sender */
memset(&s_tmp, 0, sizeof(s_tmp));
segment_size = recvfrom(agentsocket, &s_tmp, sizeof(s_tmp), 0, (struct sockaddr *)&tmp_addr, &tmp_size);
if(segment_size > 0){
inet_ntop(AF_INET, &tmp_addr.sin_addr.s_addr, ipfrom, sizeof(ipfrom));
portfrom = ntohs(tmp_addr.sin_port);
if(strcmp(ipfrom, ip[0]) == 0 && portfrom == port[0]) {
/* segment from sender, not ack */
if(s_tmp.head.ack) {
fprintf(stderr, "收到來自 sender 的 ack segment\n");
exit(1);
}
total_data++;
if(s_tmp.head.fin == 1) {
printf("get fin\n");
sendto(agentsocket, &s_tmp, segment_size, 0, (struct sockaddr *)&receiver, recv_size);
printf("fwd fin\n");
}
else {
index = s_tmp.head.seqNumber;
if(rand() % 100 < 100 * loss_rate){
drop_data++;
printf("drop data #%d, loss rate = %.4f\n", index, (float)drop_data/total_data);
} else{
printf("get data #%d\n",index);
sendto(agentsocket, &s_tmp, segment_size, 0, (struct sockaddr *)&receiver,recv_size);
printf("fwd data #%d, loss rate = %.4f\n",index,(float)drop_data/total_data);
}
}
}
else if(strcmp(ipfrom,ip[2]) == 0 && portfrom == port[2]) {
/* segment from receiver, ack */
if(s_tmp.head.ack == 0) {
fprintf(stderr, "收到來自 receiver 的 non-ack segment\n");
exit(1);
}
if(s_tmp.head.fin == 1) {
printf("get finack\n");
sendto(agentsocket, &s_tmp, segment_size, 0, (struct sockaddr *)&sender, sender_size);
printf("fwd finack\n");
break;
} else {
index = s_tmp.head.ackNumber;
printf("get ack #%d\n", index);
sendto(agentsocket, &s_tmp, segment_size, 0, (struct sockaddr *)&sender, sender_size);
printf("fwd ack #%d\n", index);
}
}
}
}
return 0;
}