diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 578d567..6b13f74 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -6,6 +6,9 @@ on:
     - master
     - develop
   pull_request:
+    branches:
+    - master
+    - develop
 
 jobs:
   Build:
diff --git a/.gitignore b/.gitignore
index 01f9cb9..8745738 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,2 @@
-build/
-.vscode/
\ No newline at end of file
+/build/
+/.vscode/
\ No newline at end of file
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 17e0766..434b1ae 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.5)
+cmake_minimum_required(VERSION 3.10)
 project(libtelnet
     VERSION 0.30.0
     LANGUAGES C
@@ -6,6 +6,11 @@ project(libtelnet
 set(PROJECT_DESCRIPTION "TELNET protocol handling library")
 set(PROJECT_HOMEPAGE_URL https://github.com/seanmiddleditch/libtelne)
 
+# Enable CMAKE Policy
+if(${CMAKE_VERSION} VERSION_LESS 3.10)
+    cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
+endif()
+
 if (MSVC)
     add_definitions(-D_SCL_SECURE_NO_WARNINGS -D_CRT_SECURE_NO_WARNINGS)
     if (LIBTELNET_STRICT)
@@ -27,6 +32,13 @@ target_include_directories(libtelnet
         ${CMAKE_CURRENT_SOURCE_DIR}
 )
 
+find_package(ZLIB)
+if(${ZLIB_FOUND})
+      target_compile_definitions(libtelnet PUBLIC HAVE_ZLIB)
+      target_include_directories(libtelnet PRIVATE ${ZLIB_INCLUDE_DIRS})
+      target_link_libraries(libtelnet PRIVATE ${ZLIB_LIBRARIES})
+endif()
+
 add_subdirectory(util)
 add_subdirectory(doc)
 add_subdirectory(test)
diff --git a/doc/CMakeLists.txt b/doc/CMakeLists.txt
index 2147c1a..5e1231a 100644
--- a/doc/CMakeLists.txt
+++ b/doc/CMakeLists.txt
@@ -1,8 +1,8 @@
 find_package(Doxygen)
 
-add_subdirectory(man)
-
 if (DOXYGEN_FOUND)
+  add_subdirectory(man)
+
   configure_file(Doxyfile.in Doxyfile)
   add_custom_target(doc_doxygen ALL
     COMMAND ${DOXYGEN_EXECUTABLE} ${DOXYGEN_OUT}
diff --git a/libtelnet.c b/libtelnet.c
index 71dc5f3..3d09e53 100644
--- a/libtelnet.c
+++ b/libtelnet.c
@@ -407,7 +407,6 @@ static void _negotiate(telnet_t *telnet, unsigned char telopt) {
 			break;
 		case Q_WANTNO_OP:
 			_set_rfc1143(telnet, telopt, Q_US(q), Q_YES);
-			NEGOTIATE_EVENT(telnet, TELNET_EV_WILL, telopt);
 			_error(telnet, __LINE__, __func__, TELNET_EPROTOCOL, 0,
 					"DONT answered by WILL");
 			break;
@@ -437,7 +436,8 @@ static void _negotiate(telnet_t *telnet, unsigned char telopt) {
 			break;
 		case Q_WANTNO_OP:
 			_set_rfc1143(telnet, telopt, Q_US(q), Q_WANTYES);
-			NEGOTIATE_EVENT(telnet, TELNET_EV_DO, telopt);
+			_send_negotiate(telnet, TELNET_DO, telopt);
+			NEGOTIATE_EVENT(telnet, TELNET_EV_WONT, telopt);
 			break;
 		case Q_WANTYES:
 		case Q_WANTYES_OP:
@@ -465,7 +465,6 @@ static void _negotiate(telnet_t *telnet, unsigned char telopt) {
 			break;
 		case Q_WANTNO_OP:
 			_set_rfc1143(telnet, telopt, Q_YES, Q_HIM(q));
-			NEGOTIATE_EVENT(telnet, TELNET_EV_DO, telopt);
 			_error(telnet, __LINE__, __func__, TELNET_EPROTOCOL, 0,
 					"WONT answered by DO");
 			break;
@@ -491,12 +490,12 @@ static void _negotiate(telnet_t *telnet, unsigned char telopt) {
 			break;
 		case Q_WANTNO:
 			_set_rfc1143(telnet, telopt, Q_NO, Q_HIM(q));
-			NEGOTIATE_EVENT(telnet, TELNET_EV_WONT, telopt);
+			NEGOTIATE_EVENT(telnet, TELNET_EV_DONT, telopt);
 			break;
 		case Q_WANTNO_OP:
 			_set_rfc1143(telnet, telopt, Q_WANTYES, Q_HIM(q));
 			_send_negotiate(telnet, TELNET_WILL, telopt);
-			NEGOTIATE_EVENT(telnet, TELNET_EV_WILL, telopt);
+			NEGOTIATE_EVENT(telnet, TELNET_EV_DONT, telopt);
 			break;
 		case Q_WANTYES:
 		case Q_WANTYES_OP:
@@ -553,7 +552,7 @@ static int _environ_telnet(telnet_t *telnet, unsigned char type,
 		ev.type = TELNET_EV_ENVIRON;
 		telnet->eh(telnet, &ev, telnet->ud);
 
-		return 1;
+		return 0;
 	}
 
 	/* very second byte must be VAR or USERVAR, if present */
@@ -657,7 +656,7 @@ static int _environ_telnet(telnet_t *telnet, unsigned char type,
 
 	/* clean up */
 	free(values);
-	return 1;
+	return 0;
 }
 
 /* process an MSSP subnegotiation buffer */
@@ -849,17 +848,14 @@ static int _subnegotiate(telnet_t *telnet) {
 	 * start handling the compressed stream if it's not already.
 	 */
 	case TELNET_TELOPT_COMPRESS2:
-		if (telnet->sb_telopt == TELNET_TELOPT_COMPRESS2) {
-			if (_init_zlib(telnet, 0, 1) != TELNET_EOK)
-				return 0;
+		if (_init_zlib(telnet, 0, 1) != TELNET_EOK)
+			return 0;
 
-			/* notify app that compression was enabled */
-			ev.type = TELNET_EV_COMPRESS;
-			ev.compress.state = 1;
-			telnet->eh(telnet, &ev, telnet->ud);
-			return 1;
-		}
-		return 0;
+		/* notify app that compression was enabled */
+		ev.type = TELNET_EV_COMPRESS;
+		ev.compress.state = 1;
+		telnet->eh(telnet, &ev, telnet->ud);
+		return 1;
 #endif /* defined(HAVE_ZLIB) */
 
 	/* specially handled subnegotiation telopt types */
@@ -1613,6 +1609,9 @@ void telnet_ttype_send(telnet_t *telnet) {
 void telnet_ttype_is(telnet_t *telnet, const char* ttype) {
 	static const unsigned char IS[] = { TELNET_IAC, TELNET_SB,
 			TELNET_TELOPT_TTYPE, TELNET_TTYPE_IS };
+	if (!ttype) {
+		ttype = "NVT";
+	}
 	_sendu(telnet, IS, sizeof(IS));
 	_send(telnet, ttype, strlen(ttype));
 	telnet_finish_sb(telnet);
diff --git a/util/telnet-chatd.c b/util/telnet-chatd.c
index 96800fa..12cf44a 100644
--- a/util/telnet-chatd.c
+++ b/util/telnet-chatd.c
@@ -167,6 +167,7 @@ static void _online(const char *line, size_t overflow, void *ud) {
 		_message(user->name, "** HAS QUIT **");
 		free(user->name);
 		user->name = 0;
+		telnet_free(user->telnet);
 		return;
 	}
 
@@ -177,7 +178,7 @@ static void _online(const char *line, size_t overflow, void *ud) {
 static void _input(struct user_t *user, const char *buffer,
 		size_t size) {
 	unsigned int i;
-	for (i = 0; i != size; ++i)
+	for (i = 0; user->sock != -1 && i != size; ++i)
 		linebuffer_push(user->linebuf, sizeof(user->linebuf), &user->linepos,
 				(char)buffer[i], _online, user);
 }
@@ -307,7 +308,7 @@ int main(int argc, char **argv) {
 		}
 
 		/* new connection */
-		if (pfd[MAX_USERS].revents & POLLIN) {
+		if (pfd[MAX_USERS].revents & (POLLIN | POLLERR | POLLHUP)) {
 			/* acept the sock */
 			addrlen = sizeof(addr);
 			if ((client_sock = accept(listen_sock, (struct sockaddr *)&addr,
@@ -345,20 +346,19 @@ int main(int argc, char **argv) {
 			if (users[i].sock == -1)
 				continue;
 
-			if (pfd[i].revents & POLLIN) {
+			if (pfd[i].revents & (POLLIN | POLLERR | POLLHUP)) {
 				if ((rs = recv(users[i].sock, buffer, sizeof(buffer), 0)) > 0) {
 					telnet_recv(users[i].telnet, buffer, rs);
 				} else if (rs == 0) {
 					printf("Connection closed.\n");
 					close(users[i].sock);
+					users[i].sock = -1;
 					if (users[i].name != 0) {
 						_message(users[i].name, "** HAS DISCONNECTED **");
 						free(users[i].name);
 						users[i].name = 0;
 					}
 					telnet_free(users[i].telnet);
-					users[i].sock = -1;
-					break;
 				} else if (errno != EINTR) {
 					fprintf(stderr, "recv(client) failed: %s\n",
 							strerror(errno));
diff --git a/util/telnet-client.c b/util/telnet-client.c
index aff4558..5c0a7f8 100644
--- a/util/telnet-client.c
+++ b/util/telnet-client.c
@@ -225,7 +225,7 @@ int main(int argc, char **argv) {
 	/* loop while both connections are open */
 	while (poll(pfd, 2, -1) != -1) {
 		/* read from stdin */
-		if (pfd[0].revents & POLLIN) {
+		if (pfd[0].revents & (POLLIN | POLLERR | POLLHUP)) {
 			if ((rs = read(STDIN_FILENO, buffer, sizeof(buffer))) > 0) {
 				_input(buffer, rs);
 			} else if (rs == 0) {
@@ -238,7 +238,7 @@ int main(int argc, char **argv) {
 		}
 
 		/* read from client */
-		if (pfd[1].revents & POLLIN) {
+		if (pfd[1].revents & (POLLIN | POLLERR | POLLHUP)) {
 			if ((rs = recv(sock, buffer, sizeof(buffer), 0)) > 0) {
 				telnet_recv(telnet, buffer, rs);
 			} else if (rs == 0) {
diff --git a/util/telnet-proxy.c b/util/telnet-proxy.c
index 32d393d..16d8a33 100644
--- a/util/telnet-proxy.c
+++ b/util/telnet-proxy.c
@@ -464,7 +464,7 @@ int main(int argc, char **argv) {
 		/* loop while both connections are open */
 		while (poll(pfd, 2, -1) != -1) {
 			/* read from server */
-			if (pfd[0].revents & POLLIN) {
+			if (pfd[0].revents & (POLLIN | POLLERR | POLLHUP)) {
 				if ((rs = recv(server.sock, buffer, sizeof(buffer), 0)) > 0) {
 					telnet_recv(server.telnet, buffer, rs);
 				} else if (rs == 0) {
@@ -480,7 +480,7 @@ int main(int argc, char **argv) {
 			}
 
 			/* read from client */
-			if (pfd[1].revents & POLLIN) {
+			if (pfd[1].revents & (POLLIN | POLLERR | POLLHUP)) {
 				if ((rs = recv(client.sock, buffer, sizeof(buffer), 0)) > 0) {
 					telnet_recv(client.telnet, buffer, rs);
 				} else if (rs == 0) {