diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7adbda0..ab97920 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.10)
+cmake_minimum_required(VERSION 3.9)
 project(esc C)
 
 set(CMAKE_C_STANDARD 99)
@@ -8,7 +8,7 @@ if(WIN32)
     link_directories(c:/Users/nicol/dev/thirdparty/protobuf-c/protobuf-c/.libs)
 endif()
 
-add_executable(esc src/main.c src/utils/mutex.c src/utils/mutex.h src/utils/thread.c src/utils/thread.h src/utils/socket.c src/utils/socket.h src/esc.c src/esc.h src/proto.c src/proto.h src/utils/uuid.c src/utils/uuid.h src/utils/buffer.c src/utils/buffer.h src/tcp_package.c src/tcp_package.h)
+add_executable(esc src/main.c src/utils/mutex.c src/utils/mutex.h src/utils/thread.c src/utils/thread.h src/utils/socket.c src/utils/socket.h src/esc.c src/esc.h src/proto.c src/proto.h src/utils/uuid.c src/utils/uuid.h src/utils/buffer.c src/utils/buffer.h src/tcp_package.c src/tcp_package.h src/utils/string.c src/utils/string.h)
 
 if(WIN32)
     target_link_libraries(esc wsock32 ws2_32 libprotobuf-c.a)
diff --git a/src/esc.c b/src/esc.c
index f91fbbf..cb54fb7 100644
--- a/src/esc.c
+++ b/src/esc.c
@@ -14,12 +14,11 @@
 #include "tcp_package.h"
 #include "utils/thread.h"
 #include "utils/mutex.h"
+#include "utils/string.h"
 
-const char* string_copy(const char *src) {
-    char* dst = malloc(strlen(src)+1);
-    strcpy(dst, src);
-    return dst;
-}
+#ifdef _WIN32
+#define sleep Sleep
+#endif
 
 typedef int bool_t;
 const bool_t BOOL_TRUE = 1;
@@ -68,7 +67,11 @@ struct st_connection {
     socket_t tcp_conn;
     ProtobufCAllocator protobuf_c_allocator;
     thread_t manager_thread;
-    mutex_t mutex_lock;
+	mutex_t sending_lock;
+    mutex_t send_lock;
+    tcp_package_t* send_pkg;
+    mutex_t recv_lock;
+    tcp_package_t* recv_pkg;
 };
 
 struct st_static_endpoint_discoverer {
@@ -89,7 +92,7 @@ const node_endpoints_t* static_discover(const static_endpoint_discoverer_t* disc
 
 int connection_send_tcp_package(const esc_connection_t* conn, const tcp_package_t* pkg) {
     char uuid_buf[37];
-    printf("connection_send_tcp_package: %u %u %s %lu\n", pkg->command, pkg->flags, esc_uuid_format(&pkg->correlation_id, uuid_buf, 37), pkg->data.size);
+    fprintf(stderr, "connection_send_tcp_package: %u %u %s %lu\n", pkg->command, pkg->flags, esc_uuid_format(&pkg->correlation_id, uuid_buf, 37), pkg->data.size);
     buffer_t send_buffer = tcp_package_to_buffer(pkg);
     uint32_t size = (uint32_t)send_buffer.size;
     if (socket_send(conn->tcp_conn, (char *) &size, sizeof(uint32_t)) <= 0) {
@@ -108,7 +111,7 @@ const tcp_package_t* connection_recv_tcp_package(const esc_connection_t* conn) {
     uint32_t recv_size;
     ssize_t rc;
     if ((rc = socket_recv(conn->tcp_conn, (char *)&recv_size, sizeof(uint32_t))) != 4) {
-        printf("%ld %d", rc, socket_error());
+        fprintf(stderr, "%ld %d", rc, socket_error());
         return 0;
     }
     buffer_t recv_buffer = buffer_create(recv_size);
@@ -120,7 +123,7 @@ const tcp_package_t* connection_recv_tcp_package(const esc_connection_t* conn) {
     const tcp_package_t* recv_pkg = tcp_package_from_buffer(recv_buffer);
     buffer_free(recv_buffer);
     char uuid_buf[37];
-    printf("connection_recv_tcp_package: %u %u %s %lu\n", recv_pkg->command, recv_pkg->flags, esc_uuid_format(&recv_pkg->correlation_id, uuid_buf, 37), recv_pkg->data.size);
+    fprintf(stderr, "connection_recv_tcp_package: %u %u %s %lu\n", recv_pkg->command, recv_pkg->flags, esc_uuid_format(&recv_pkg->correlation_id, uuid_buf, 37), recv_pkg->data.size);
     //for (int32_t i=0;i<recv_pkg->data.size;i++) {
     //    printf("%x (%c) ", recv_pkg->data.data[i], recv_pkg->data.data[i]);
     //}
@@ -128,6 +131,27 @@ const tcp_package_t* connection_recv_tcp_package(const esc_connection_t* conn) {
     return recv_pkg;
 }
 
+void connection_enqueue_send(esc_connection_t* conn, tcp_package_t* pkg) {
+    mutex_lock(conn->sending_lock);	
+	mutex_lock(conn->send_lock);
+    conn->send_pkg = pkg;
+	mutex_unlock(conn->send_lock);
+}
+
+tcp_package_t* connection_wait_for(esc_connection_t* conn, esc_uuid_t* correlation_id) {
+    tcp_package_t* found = 0;
+    while(found == 0) {
+        mutex_lock(conn->recv_lock);
+        if (conn->recv_pkg && esc_uuid_compare(&conn->recv_pkg->correlation_id, correlation_id) == 0) {
+            found = conn->recv_pkg;
+			conn->recv_pkg = 0;
+        }
+        mutex_unlock(conn->recv_lock);
+		sleep(10);
+    }
+    return found;
+}
+
 void* protobuf_c_alloc(void *alloc_data, size_t size) {
     return malloc(size);
 }
@@ -164,24 +188,53 @@ const esc_connection_t* esc_connection_create(const esc_connection_settings_t* c
         char buf[40];
         esc_uuid_format(uuid, buf, 40);
         conn->name = string_copy(buf);
-        free(uuid);
+        esc_uuid_free(uuid);
     } else {
         conn->name = connection_name;
     }
+	conn->recv_pkg = 0;
+	conn->send_pkg = 0;
+	conn->send_lock = mutex_create();
+	conn->sending_lock = mutex_create();
+	conn->recv_lock = mutex_create();
     return conn;
 }
 
 void* connection_thread(void* arg) {
-    const esc_connection_t* conn = arg;
+    esc_connection_t* conn = arg;
 
     while(1) {
-        //mutex_lock(conn->mutex_lock);
-        //if (socket_readable(conn->tcp_conn)) {
-
-        //}
+        mutex_lock(conn->send_lock);
+		//printf("%p ", conn->send_pkg);		
+		int rc;
+        if (conn->send_pkg) {
+			if ((rc = connection_send_tcp_package(conn, conn->send_pkg)) == 0) {
+				// free send pkg
+				conn->send_pkg = 0;
+				mutex_unlock(conn->sending_lock);
+			}
+        }
+		mutex_unlock(conn->send_lock);
+		
+		if ((rc = socket_readable(conn->tcp_conn)) > 0) {
+			mutex_lock(conn->recv_lock);
+			if (conn->recv_pkg == 0) {
+				conn->recv_pkg = connection_recv_tcp_package(conn);
+			}
+			mutex_unlock(conn->recv_lock);
+		}
+		//printf("%d ", rc);
+		
+		mutex_lock(conn->recv_lock);
+		if (conn->recv_pkg && conn->recv_pkg->command == 0x01) {
+			tcp_package_t* hb = tcp_package_create(0x02, &conn->recv_pkg->correlation_id, buffer_create(0));
+			conn->recv_pkg = 0;
+			connection_send_tcp_package(conn, hb);
+		}
+		mutex_unlock(conn->recv_lock);
 
         //mutex_unlock(conn->mutex_lock);
-        sleep(1);
+        sleep(10);
     }
 }
 
@@ -200,7 +253,12 @@ int esc_connection_connect(const esc_connection_t* conn) {
     if (socket_connect(conn->tcp_conn, endpoint.host, endpoint.port) != 0) {
         return -2;
     }
-    // Identify
+	// Start manager thread
+    _conn->manager_thread = thread_create(connection_thread, _conn);
+    if (thread_start(_conn->manager_thread)) {
+        return -3;
+    }
+	// Identify
     // build message
     EventStore__Client__Messages__IdentifyClient identify_client;
     event_store__client__messages__identify_client__init(&identify_client);
@@ -211,24 +269,13 @@ int esc_connection_connect(const esc_connection_t* conn) {
     event_store__client__messages__identify_client__pack(&identify_client, buffer);
     // build tcp_package
     const tcp_package_t* send_pkg = tcp_package_create(0xF5, esc_uuid_create(), buffer_from(buffer, s));
-    if (connection_send_tcp_package(conn, send_pkg) != 0) {
-        return -3;
-    }
-    const tcp_package_t* recv_pkg = connection_recv_tcp_package(conn);
-    if (recv_pkg == 0) {
-        return -4;
-    }
+    connection_enqueue_send(_conn, send_pkg);
+	const tcp_package_t* recv_pkg = connection_wait_for(_conn, &send_pkg->correlation_id);
     if (recv_pkg->command != 0xF6) {
         return -5;
     }
-
-    _conn->mutex_lock = mutex_create();
-    _conn->manager_thread = thread_create(connection_thread, _conn);
-    if (thread_start(_conn->manager_thread)) {
-        return -6;
-    }
-
-    return 0;
+	
+	return 0;
 }
 
 const esc_credentials_t* esc_credentials_create(const char* username, const char* password) {
@@ -246,8 +293,8 @@ const esc_recorded_event_t* recorded_event_create(EventStore__Client__Messages__
     ev->event_number = msg->event_number;
     ev->event_stream_id = string_copy(msg->event_stream_id);
     ev->created_epoch = msg->has_created_epoch ? msg->created_epoch : 0;
-    ev->data = buffer_copyfrom(msg->data.data, msg->data.len);
-    ev->metadata = buffer_copyfrom(msg->metadata.data, msg->metadata.len);
+    ev->data = buffer_from(msg->data.data, msg->data.len);
+    ev->metadata = buffer_from(msg->metadata.data, msg->metadata.len);
 
     return ev;
 }
@@ -273,14 +320,9 @@ const esc_all_events_slice_t* esc_connection_read_all_forward(const esc_connecti
     uint8_t buffer[s];
     event_store__client__messages__read_all_events__pack(&send_msg, buffer);
     const tcp_package_t* send_pkg = tcp_package_create_authenticated(0xB6, esc_uuid_create(), buffer_from(buffer, s), credentials->username, credentials->password);
-    if (connection_send_tcp_package(conn, send_pkg) != 0) {
-        return 0;
-    }
+    connection_enqueue_send(conn, send_pkg);
 
-    const tcp_package_t* recv_pkg = connection_recv_tcp_package(conn);
-    if (recv_pkg == 0) {
-        return 0;
-    }
+    const tcp_package_t* recv_pkg = connection_wait_for(conn, &send_pkg->correlation_id);
     if (recv_pkg->command != 0xB7) {
         return 0;
     }
diff --git a/src/main.c b/src/main.c
index 664bfb7..af1eeb6 100644
--- a/src/main.c
+++ b/src/main.c
@@ -9,7 +9,7 @@ int main() {
     WSAStartup(MAKEWORD(2,0), &wsaData);
 #endif
 
-    const esc_connection_t* conn = esc_connection_create(esc_default_connection_settings, "tcp://127.0.0.1:1113", NULL);
+	const esc_connection_t* conn = esc_connection_create(esc_default_connection_settings, "tcp://127.0.0.1:1113", NULL);
     if (conn == 0) {
         return -1;
     }
@@ -40,6 +40,12 @@ int main() {
                    result->events[i]->event->metadata.size);
         }
     } while(result->is_end_of_stream == 0);
+	
+#ifdef _WIN32
+	Sleep(30000);
+#else
+	sleep(30000);
+#endif
 
     esc_connection_close(conn);
 
diff --git a/src/utils/buffer.c b/src/utils/buffer.c
index 1d4a831..a920e2e 100644
--- a/src/utils/buffer.c
+++ b/src/utils/buffer.c
@@ -16,9 +16,9 @@ const buffer_t buffer_from(uint8_t* data, size_t size) {
     return buf;
 }
 
-const buffer_t buffer_copyfrom(uint8_t* data, size_t size) {
-    buffer_t buf = {size, malloc(size)};
-    memcpy(buf.data, data, size);
+const buffer_t buffer_copy(const buffer_t* other) {
+    buffer_t buf = {other->size, malloc(other->size)};
+    memcpy(buf.data, other->data, other->size);
     return buf;
 }
 
diff --git a/src/utils/buffer.h b/src/utils/buffer.h
index 3f0b044..df0b4af 100644
--- a/src/utils/buffer.h
+++ b/src/utils/buffer.h
@@ -16,7 +16,7 @@ typedef struct st_buffer buffer_t;
 
 const buffer_t buffer_create(size_t size);
 const buffer_t buffer_from(uint8_t* data, size_t size);
-const buffer_t buffer_copyfrom(uint8_t* data, size_t size);
+const buffer_t buffer_copy(const buffer_t* other);
 void buffer_free(buffer_t buffer);
 
 #endif //ESC_BUFFER_H
diff --git a/src/utils/socket.c b/src/utils/socket.c
index a72f213..5e0982d 100644
--- a/src/utils/socket.c
+++ b/src/utils/socket.c
@@ -3,13 +3,7 @@
 //
 
 #include <stdlib.h>
-#include <sys/socket.h>
-#include <netinet/in.h>
 #include <unistd.h>
-#include <netdb.h>
-#include <string.h>
-#include <errno.h>
-#include <stdio.h>
 #include "socket.h"
 
 #ifdef _WIN32
@@ -55,12 +49,20 @@ int socket_connect(socket_t s, char* addr, unsigned short port) {
     return connect(s->s, result->ai_addr, (int)result->ai_addrlen);
 }
 
-int socket_send(socket_t s, char* data, int len) {
-    return send(s->s, data, len, 0);
+ssize_t socket_send(socket_t s, char* data, size_t len) {
+    return send(s->s, data, (int)len, 0);
 }
 
-int socket_recv(socket_t s, char* buf, int len) {
-    return recv(s->s, buf, len, 0);
+ssize_t socket_recv(socket_t s, char* buf, size_t len) {
+    return recv(s->s, buf, (int)len, 0);
+}
+
+int socket_readable(socket_t s) {
+	fd_set readable;
+	FD_SET(s->s, &readable);
+	struct timeval timeout = {0, 0};
+	
+	return select(0, &readable, 0, 0, &timeout);
 }
 
 int socket_error() {
@@ -68,6 +70,13 @@ int socket_error() {
 }
 #endif
 #ifdef __linux__
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <netdb.h>
+#include <string.h>
+#include <errno.h>
+#include <stdio.h>
+
 struct st_socket {
     int s;
     int af;
diff --git a/src/utils/socket.h b/src/utils/socket.h
index 7f0c9f0..36e52aa 100644
--- a/src/utils/socket.h
+++ b/src/utils/socket.h
@@ -18,6 +18,7 @@ void socket_close(socket_t s);
 int socket_connect(socket_t s, char* addr, unsigned short port);
 ssize_t socket_send(socket_t s, char* data, size_t len);
 ssize_t socket_recv(socket_t s, char* buf, size_t len);
+int socket_readable(socket_t s);
 int socket_error();
 
 #endif //ESC_SOCKET_H
diff --git a/src/utils/string.c b/src/utils/string.c
new file mode 100644
index 0000000..7652a50
--- /dev/null
+++ b/src/utils/string.c
@@ -0,0 +1,13 @@
+//
+// Created by nicol on 2018-03-19.
+//
+
+#include <stdlib.h>
+#include <string.h>
+#include "string.h"
+
+const char* string_copy(const char *src) {
+    char* dst = malloc(strlen(src)+1);
+    strcpy(dst, src);
+    return dst;
+}
diff --git a/src/utils/string.h b/src/utils/string.h
new file mode 100644
index 0000000..141e61a
--- /dev/null
+++ b/src/utils/string.h
@@ -0,0 +1,10 @@
+//
+// Created by nicol on 2018-03-19.
+//
+
+#ifndef ESC_STRING_H
+#define ESC_STRING_H
+
+const char* string_copy(const char *src);
+
+#endif //ESC_STRING_H
diff --git a/src/utils/thread.c b/src/utils/thread.c
index 8f799f5..935acdc 100644
--- a/src/utils/thread.c
+++ b/src/utils/thread.c
@@ -6,30 +6,54 @@
 #include "thread.h"
 
 #ifdef _WIN32
+#include <windows.h>
+
+struct st_thread {
+    DWORD   id;
+    HANDLE  handle;
+    thread_start_t start;
+    thread_arg_t arg;
+    int     last_error;
+};
+
 thread_t thread_create(thread_start_t thread_start, thread_arg_t thread_arg) {
     thread_t thread = malloc(sizeof(struct st_thread));
-    thread->handle = CreateThread(NULL, 0, thread_start, thread_arg, CREATE_SUSPENDED, &thread->id);
-    if (thread->handle == NULL) {
-        free(thread);
-        return NULL;
-    }
+    thread->handle = 0;
+    thread->start = thread_start;
+    thread->arg = thread_arg;
+    thread->last_error = 0;
     return thread;
 }
 
 int thread_start(thread_t thread) {
-    if (ResumeThread(thread->handle) == -1) return -1;
+    thread->handle = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)thread->start, thread->arg, 0, &thread->id);
+    if (thread->handle == NULL) {
+        DWORD rc = GetLastError();
+        thread->last_error = (int)rc;
+        return (int)rc;
+    }
     return 0;
 }
 
 int thread_wait(thread_t thread) {
-    if (WaitForSingleObject(thread->handle, INFINITE) != WAIT_OBJECT_0) return -1;
+    if (WaitForSingleObject(thread->handle, INFINITE) == WAIT_FAILED) {
+        DWORD rc = GetLastError();
+        thread->last_error = (int)rc;
+        return (int)rc;
+    }
     return 0;
 }
 
 int thread_destroy(thread_t thread) {
     if (thread_wait(thread) != 0) SuspendThread(thread->handle);
     CloseHandle(thread->handle);
+    free(thread);
 }
+
+int thread_error(thread_t thread) {
+    return thread->last_error;
+}
+
 #endif
 #ifdef __linux__
 #include <pthread.h>
diff --git a/src/utils/thread.h b/src/utils/thread.h
index bb92c0a..f115929 100644
--- a/src/utils/thread.h
+++ b/src/utils/thread.h
@@ -5,16 +5,6 @@
 #ifndef ESC_THREAD_H
 #define ESC_THREAD_H
 
-#ifdef _WIN32
-#include <windows.h>
-struct st_thread {
-    DWORD   id;
-    HANDLE  handle;
-};
-typedef struct st_thread* thread_t;
-typedef LPTHREAD_START_ROUTINE thread_start_t;
-typedef LPVOID thread_arg_t;
-#endif
 typedef void* (*thread_start_t)(void*);
 typedef void* thread_arg_t;
 typedef struct st_thread* thread_t;
diff --git a/src/utils/uuid.c b/src/utils/uuid.c
index 4f33c35..dab003f 100644
--- a/src/utils/uuid.c
+++ b/src/utils/uuid.c
@@ -5,19 +5,26 @@
 #include <stdlib.h>
 #include <time.h>
 #include <stdio.h>
+#include <memory.h>
 #include "uuid.h"
 
+#define UUID_SIZE 16
+
 //TODO: fixme - this is not secure, use crypto random bytes instead of rand
 const esc_uuid_t* esc_uuid_create() {
     esc_uuid_t* result = malloc(sizeof(esc_uuid_t));
     srand(time(NULL));
-    for(int i=0;i<16;i++)
+    for(int i=0;i<UUID_SIZE;i++)
         result->data[i] = (uint8_t)(rand() & 0xff);
     return result;
 }
 
+void esc_uuid_free(const esc_uuid_t* uuid) {
+    free((void*)uuid);
+}
+
 const esc_uuid_t* esc_uuid_from(uint8_t* src, size_t size) {
-    if (size != 16) {
+    if (size != UUID_SIZE) {
         return 0;
     }
     esc_uuid_t* uuid = malloc(sizeof(esc_uuid_t));
@@ -26,6 +33,14 @@ const esc_uuid_t* esc_uuid_from(uint8_t* src, size_t size) {
     return uuid;
 }
 
+const esc_uuid_t* esc_uuid_copy(const esc_uuid_t* other) {
+    return esc_uuid_from((uint8_t*)&other->data, UUID_SIZE);
+}
+
+int esc_uuid_compare(const esc_uuid_t* left, const esc_uuid_t* right) {
+    return memcmp(left->data, right->data, UUID_SIZE);
+}
+
 const char* esc_uuid_format(const esc_uuid_t* uuid, char* buffer, size_t buf_size) {
     snprintf(buffer, buf_size, "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x",
              uuid->data[0],
diff --git a/src/utils/uuid.h b/src/utils/uuid.h
index b54c9e3..9c737ac 100644
--- a/src/utils/uuid.h
+++ b/src/utils/uuid.h
@@ -13,7 +13,10 @@ struct st_uuid {
 typedef struct st_uuid esc_uuid_t;
 
 const esc_uuid_t* esc_uuid_create();
+void esc_uuid_free(const esc_uuid_t* uuid);
 const esc_uuid_t* esc_uuid_from(uint8_t* src, size_t size);
+const esc_uuid_t* esc_uuid_copy(const esc_uuid_t* other);
+int esc_uuid_compare(const esc_uuid_t* left, const esc_uuid_t* right);
 const char* esc_uuid_format(const esc_uuid_t* uuid, char* buffer, size_t buf_size);
 
 #endif //ESC_UUID_H