diff --git a/kernel/defs.h b/kernel/defs.h
index d133cd3..befab4f 100644
--- a/kernel/defs.h
+++ b/kernel/defs.h
@@ -237,3 +237,4 @@ void            netinit(void);
 void            net_rx(char *buf, int len);
 
 #endif
+#define DEBUG_INFO printf("File: %s, Line: %d\n", __FILE__, __LINE__)
diff --git a/kernel/net.c b/kernel/net.c
index e7e61f9..b0078d3 100644
--- a/kernel/net.c
+++ b/kernel/net.c
@@ -24,11 +24,11 @@ netinit(void)
 {
   initlock(&netlock, "netlock");
 }
-#define MAXPORT 65536
+#define MAXPORT 10000+1
 #define MAXCNT 16
-void *udpq[MAXPORT][MAXCNT];
-int udpc[MAXPORT];
-int pused[MAXPORT];
+static void *udpq[MAXPORT][MAXCNT];
+static char udph[MAXPORT],udpt[MAXPORT],udpc[MAXPORT];
+static int pused[MAXPORT];
 
 //
 // bind(int port)
@@ -85,29 +85,44 @@ sys_recv(void)
   //
   acquire(&netlock);
   struct proc *p = myproc();
-  short dport;
+  int dport;
   uint64 src,sport,buf;
   int maxlen;
   argint(0, (int*)&dport);
   argaddr(1, &src);
-  argaddr(2,&sport);
-  argaddr(3,&buf);
+  argaddr(2, &sport);
+  argaddr(3, &buf);
   argint(4, &maxlen);
-  if(!udpc[dport])
+  while(!udpc[dport]){
+    if(p->killed)
+      goto err;
     sleep(&udpc[dport], &netlock);
-  struct eth *eth=(struct eth *)udpq[dport][udpc[dport]];
+    if(p->killed)
+      goto err;
+  }
+  struct eth *eth=(struct eth *)udpq[dport][(int)udph[dport]];
   struct ip *ip=(struct ip *)(eth+1);
   struct udp *udp=(struct udp *)(ip+1);
-  *(int *)src=ntohl(ip->ip_src);
-  *(int *)sport=ntohs(udp->sport);
-  char *payload=(char *)(udp+1);
-  const int len=udp->ulen-sizeof(struct udp);
-  if(len>maxlen)
+  const int srcbuf=ntohl(ip->ip_src);
+  const short sportbuf=ntohs(udp->sport);
+  if(copyout(p->pagetable,src,(char *)&srcbuf,sizeof(int))<0){
     goto err;
-  if(copyout(p->pagetable,buf,payload,maxlen)<0)
-      goto err;
+  }
+  if(copyout(p->pagetable,sport,(char *)&sportbuf,sizeof(short))<0){
+    goto err;
+  }
+  char *payload=(char *)(udp+1);
+  const int len=ntohs(udp->ulen)-sizeof(struct udp);
+
+  if(len>maxlen){
+    goto err;
+  }
+  if(copyout(p->pagetable,buf,payload,len)<0){
+    goto err;
+  }
   kfree(eth);
   --udpc[dport];
+  udph[dport]=(udph[dport]+1)%MAXCNT;
   release(&netlock);
   return len;
   err:
@@ -153,6 +168,7 @@ in_cksum(const unsigned char *addr, int len)
 //
 // send(int sport, int dst, int dport, char *buf, int len)
 //
+
 uint64
 sys_send(void)
 {
@@ -168,11 +184,9 @@ sys_send(void)
   argint(2, &dport);
   argaddr(3, &bufaddr);
   argint(4, &len);
-
   int total = len + sizeof(struct eth) + sizeof(struct ip) + sizeof(struct udp);
   if(total > PGSIZE)
     return -1;
-
   char *buf = kalloc();
   if(buf == 0){
     printf("sys_send: kalloc failed\n");
@@ -210,7 +224,6 @@ sys_send(void)
   }
 
   e1000_transmit(buf, total);
-
   return 0;
 }
 
@@ -234,12 +247,16 @@ ip_rx(char *buf, int len)
   struct udp *udp=(struct udp *)(ip+1);
   const short dport=ntohs(udp->dport);
   if(!pused[dport])
-    return;
+    goto abandon;
   if(udpc[dport]==MAXCNT)
-    return;
-  udpq[dport][dport]=buf;
+    goto abandon;
+  udpq[dport][(int)udpt[dport]]=buf;//tail
+  udpt[dport]=(udpt[dport]+1)%MAXCNT;
   ++udpc[dport];
   wakeup(&udpc[dport]);
+  return;
+  abandon:
+  kfree(buf);
 }
 
 //
diff --git a/kernel/trap.c b/kernel/trap.c
index e617a0b..bf4bd1e 100644
--- a/kernel/trap.c
+++ b/kernel/trap.c
@@ -150,6 +150,7 @@ kerneltrap()
   if((which_dev = devintr()) == 0){
     // interrupt or trap from an unknown source
     printf("scause=0x%lx sepc=0x%lx stval=0x%lx\n", scause, r_sepc(), r_stval());
+    printf("pid=%d\n",myproc()->pid);
     panic("kerneltrap");
   }
 
diff --git a/time.txt b/time.txt
new file mode 100644
index 0000000..7ed6ff8
--- /dev/null
+++ b/time.txt
@@ -0,0 +1 @@
+5
diff --git a/user/nettest.c b/user/nettest.c
index 19b39ff..649d699 100644
--- a/user/nettest.c
+++ b/user/nettest.c
@@ -7,6 +7,7 @@
 #include "kernel/net.h"
 #include "kernel/stat.h"
 #include "user/user.h"
+#define DEBUG_INFO printf("File: %s, Line: %d\n", __FILE__, __LINE__)
 
 //
 // send a single UDP packet (but don't recv() the reply).
@@ -472,7 +473,6 @@ ping3()
     }
   }
   sleep(1);
-  
   //
   // send so many packets from 2008 and 2010 that some of the
   // replies must be dropped due to the requirement
@@ -493,7 +493,6 @@ ping3()
     }
   }
   sleep(1);
-
   //
   // send another packet from 2009.
   //
@@ -510,7 +509,6 @@ ping3()
       return 0;
     }
   }
-
   //
   // did both reply packets for 2009 arrive?
   //
@@ -524,7 +522,6 @@ ping3()
       fprintf(2, "ping3: recv() failed\n");
       return 0;
     }
-    
     if(src != 0x0A000202){ // 10.0.2.2
       printf("ping3: wrong ip src %x\n", src);
       return 0;
@@ -539,7 +536,6 @@ ping3()
       printf("ping3: wrong length %d\n", cc);
       return 0;
     }
-
     // printf("port=%d ii=%d: %c%c%c\n", port, ii, ibuf[0], ibuf[1], ibuf[2]);
 
     char buf[4];
@@ -581,7 +577,6 @@ ping3()
     exit(0);
   }
   close(fds[1]);
-
   sleep(5);
   static char nbuf[512];
   int n = read(fds[0], nbuf, sizeof(nbuf));
@@ -595,7 +590,6 @@ ping3()
   }
 
   printf("ping3: OK\n");
-
   return 1;
 }