From 45ce29b87474e169f50d84528a880ef988cc7a1f Mon Sep 17 00:00:00 2001
From: yash <kyash1999@gmail.com>
Date: Thu, 31 Oct 2019 23:30:42 +0530
Subject: [PATCH 1/2] client side for go back N protocol in computer networks

---
 scripts/GobackClient.java | 71 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)
 create mode 100644 scripts/GobackClient.java

diff --git a/scripts/GobackClient.java b/scripts/GobackClient.java
new file mode 100644
index 00000000..bd4edd83
--- /dev/null
+++ b/scripts/GobackClient.java
@@ -0,0 +1,71 @@
+import java.util.*;
+import java.net.*;
+import java.io.*;
+public class GobackClient {
+
+	public static void main(String[] args) throws IOException {
+		// TODO Auto-generated method stub
+		Socket s=new Socket("localhost",4001);
+		DataInputStream in=new DataInputStream(s.getInputStream());
+		DataOutputStream out=new DataOutputStream(s.getOutputStream());
+		Scanner sc=new Scanner(System.in);
+		int frame_size=10,m,res,val=0;
+		double wind;
+		m=in.readInt();
+		wind=(Math.pow(2,m))-1;
+		int []a=new int[frame_size];
+		for(int i=0;i<a.length;i++)
+		{
+			if((i-val)%wind==0 && i>0)
+			{
+				System.out.println("Enter 1 if you've received all the frames:\n");
+				res=sc.nextInt();
+				out.writeInt(res);
+				if(res!=1)
+				{
+					int j;
+					System.out.println("Enter the frame that you didn't receive:\n");
+					res=sc.nextInt();
+					out.writeInt(res);
+					//System.out.println("lets retransmit it:\n");
+					for(j=res-1;j<res-1+wind;j++)
+					{
+						a[j]=in.readInt();
+						System.out.println("received frame" + (j+1) + "is" + a[j]);
+					}
+					i=j;
+					val=(res-1)/(int)wind;
+					continue;
+				}
+				else
+				{
+					int j;
+					System.out.println("Acknowledgement has been sent for" + i);
+					int res1=in.readInt();
+					if(res1==1)
+						System.out.println("acknowledgement received\n");
+					else
+					{
+						System.out.println("Acknowledgement not received\n");
+						for(j=i-(int)wind;j<i;j++)
+						{
+							a[j]=in.readInt();
+							System.out.println("received frame(1)" + (j+1) + "is" + a[j]);
+						}
+						i=j;
+						continue;
+					}
+				}
+			}
+			if(i==a.length)
+				break;
+			a[i]=in.readInt();
+			System.out.println("received frame from server" + i);
+		}
+		in.close();
+		out.close();
+		sc.close();
+		s.close();
+	}
+
+}

From 3460c64d821ecdbc5071121995116709b90edd01 Mon Sep 17 00:00:00 2001
From: yash <kyash1999@gmail.com>
Date: Thu, 31 Oct 2019 23:38:02 +0530
Subject: [PATCH 2/2] server side for go back N protocol in computer networks

---
 scripts/GobackServer.java | 65 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)
 create mode 100644 scripts/GobackServer.java

diff --git a/scripts/GobackServer.java b/scripts/GobackServer.java
new file mode 100644
index 00000000..867ea8a6
--- /dev/null
+++ b/scripts/GobackServer.java
@@ -0,0 +1,65 @@
+import java.util.*;
+import java.net.*;
+import java.io.*;
+public class GobackServer {
+	public static void main(String args[]) throws IOException
+	{
+		ServerSocket ss=new ServerSocket(4001);
+		Socket s=ss.accept();
+		DataInputStream in=new DataInputStream(s.getInputStream());
+		DataOutputStream out=new DataOutputStream(s.getOutputStream());
+		Scanner sc=new Scanner(System.in);
+		int frame_size=10,m,res,val=0;
+		double wind;
+		int []a=new int[frame_size];
+		for(int i=0;i<frame_size;i++)
+		{
+			System.out.println("Frame no. is: "+ (i+1));
+			a[i]=sc.nextInt();
+		}
+		System.out.println("Enter the value of m:\n");
+		m=sc.nextInt();
+		wind=(Math.pow(2,m))-1;
+		out.writeInt(m);
+		for(int i=0;i<a.length;i++)
+		{
+			if((i-val)%wind==0 && i>0)
+			{
+				res=in.readInt();
+				if(res!=1)
+				{
+					int j;
+					res=in.readInt();
+					System.out.println("lets retransmit it:\n");
+					for(j=res-1;j<res-1+wind;j++)
+						out.writeInt(a[j]);
+					i=j;
+					val=(res-1)/(int)wind;
+					continue;
+				}
+				else
+				{
+					System.out.println("Enter 1 if You've received the acknowledgement for the frame"+ i + ":\n ");
+					res=sc.nextInt();
+					out.writeInt(res);
+					if(res!=1)
+					{
+						int j;
+						for(j=res-1;j<res-1+wind;j++)
+							out.writeInt(a[j]);
+						i=j;
+						continue;
+					}
+				}
+			}
+			if(i==a.length)
+				break;
+			out.writeInt(a[i]);
+		}
+		in.close();
+		out.close();
+		sc.close();
+		s.close();
+		ss.close();
+	}
+}