From 08d8317c98c966f93dc74e7bf37e4a7541e2bf47 Mon Sep 17 00:00:00 2001
From: Dominik Downarowicz <dominik.downarowicz@sonepar.at>
Date: Tue, 1 Mar 2022 15:00:45 +0100
Subject: [PATCH] Add UnNegotiateTelnet Function

---
 pom.xml                                       |  2 +-
 .../java/at/downardo/j3270Server/Telnet.java  | 40 +++++++++++++++++++
 2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/pom.xml b/pom.xml
index ccf5be2..e078f1e 100644
--- a/pom.xml
+++ b/pom.xml
@@ -2,7 +2,7 @@
   <modelVersion>4.0.0</modelVersion>
   <groupId>at.downardo</groupId>
   <artifactId>j3270Server</artifactId>
-  <version>0.0.3</version>
+  <version>0.0.4</version>
   <name>Java 3270 Server</name>
   <packaging>jar</packaging>
   <description>This libary allows the user to write servers for IBM 3270 Terminal emulators.</description>
diff --git a/src/main/java/at/downardo/j3270Server/Telnet.java b/src/main/java/at/downardo/j3270Server/Telnet.java
index 58d9d14..e07fb5e 100644
--- a/src/main/java/at/downardo/j3270Server/Telnet.java
+++ b/src/main/java/at/downardo/j3270Server/Telnet.java
@@ -26,6 +26,46 @@ public class Telnet {
 	private static final byte TERMINALTYPE = (byte)0x18;
 	private static final byte EOR = (byte)0x19;
 	
+	/**
+	 * UnNegotiateTelnet will naively (e.g. not checking client responses) attempt
+	 * to restore the telnet options state to what it was before NegotiateTelnet()
+	 * was called.
+	 * @param out
+	 * @param in
+	 */
+	public static void UnNegotiateTelnet(BufferedOutputStream out, BufferedInputStream in) {
+		byte[] _trash = new byte[255];
+		byte[] _t = {IAC,WONT,EOR,IAC,WONT,BINARY};
+		
+		try {
+			out.write(_t);
+			out.flush();
+			in.read(_trash);
+			
+			byte[] _2t = {IAC,DONT,BINARY};
+			out.write(_2t);
+			out.flush();
+
+			in.read(_trash);
+
+			byte[] _3t = {IAC,DONT,EOR};
+
+			out.write(_3t);
+			out.flush();
+
+			in.read(_trash);
+
+			byte[] _4t = {IAC,DONT,TERMINALTYPE};
+			
+			out.write(_4t);
+			out.flush();
+
+			in.read(_trash);
+
+		} catch (IOException e) {
+			e.printStackTrace();
+		}
+	}
 	
 	
 	/**