diff --git a/server/src/core/client.cpp b/server/src/core/client.cpp
index b0b3fd53..a277a6ad 100644
--- a/server/src/core/client.cpp
+++ b/server/src/core/client.cpp
@@ -29,6 +29,7 @@
 
 Client::Client(Traintastic& server, const std::string& id, boost::asio::ip::tcp::socket socket) :
   m_server{server},
+  m_strand{Traintastic::instance->ioContext()},
   m_socket(std::move(socket)),
   m_id{id},
   m_authenticated{false}//,
@@ -54,7 +55,11 @@ Client::~Client()
 
 void Client::start()
 {
-  doReadHeader();
+  m_strand.post(
+    [this]()
+    {
+      doReadHeader();
+    });
 }
 
 void Client::doReadHeader()
@@ -62,28 +67,29 @@ void Client::doReadHeader()
   auto self(shared_from_this());
   boost::asio::async_read(m_socket,
     boost::asio::buffer(&m_readBuffer.header, sizeof(m_readBuffer.header)),
-    [this, self](const boost::system::error_code& e, std::size_t)
-    {
-      if(!e)
-      {
-        m_readBuffer.message.reset(new Message(m_readBuffer.header));
-        if(m_readBuffer.message->dataSize() == 0)
+      m_strand.wrap(
+        [this, self](const boost::system::error_code& e, std::size_t)
         {
-          if(m_readBuffer.message->command() != Message::Command::Ping)
-            EventLoop::call(&Client::processMessage, this, m_readBuffer.message);
+          if(!e)
+          {
+            m_readBuffer.message.reset(new Message(m_readBuffer.header));
+            if(m_readBuffer.message->dataSize() == 0)
+            {
+              if(m_readBuffer.message->command() != Message::Command::Ping)
+                EventLoop::call(&Client::processMessage, this, m_readBuffer.message);
+              else
+                {} // TODO: ping hier replyen
+              m_readBuffer.message.reset();
+              doReadHeader();
+            }
+            else
+              doReadData();
+          }
+          else if(e == boost::asio::error::eof || e == boost::asio::error::connection_aborted || e == boost::asio::error::connection_reset)
+            connectionLost();
           else
-            {} // TODO: ping hier replyen
-          m_readBuffer.message.reset();
-          doReadHeader();
-        }
-        else
-          doReadData();
-      }
-      else if(e == boost::asio::error::eof || e == boost::asio::error::connection_aborted || e == boost::asio::error::connection_reset)
-        connectionLost();
-      else
-        connectionError("readheader", e.message());
-    });
+            connectionError("readheader", e.message());
+        }));
 }
 
 void Client::doReadData()
@@ -91,39 +97,41 @@ void Client::doReadData()
   auto self(shared_from_this());
   boost::asio::async_read(m_socket,
     boost::asio::buffer(m_readBuffer.message->data(), m_readBuffer.message->dataSize()),
-      [this, self](const boost::system::error_code& ec, std::size_t)
-      {
-        if(!ec)
+      m_strand.wrap(
+        [this, self](const boost::system::error_code& ec, std::size_t)
         {
-          if(m_readBuffer.message->command() != Message::Command::Ping)
-            EventLoop::call(&Client::processMessage, this, m_readBuffer.message);
+          if(!ec)
+          {
+            if(m_readBuffer.message->command() != Message::Command::Ping)
+              EventLoop::call(&Client::processMessage, this, m_readBuffer.message);
+            else
+            {} // TODO: ping hier replyen
+            m_readBuffer.message.reset();
+            doReadHeader();
+          }
+          else if(ec == boost::asio::error::eof || ec == boost::asio::error::connection_aborted || ec == boost::asio::error::connection_reset)
+            connectionLost();
           else
-          {} // TODO: ping hier replyen
-          m_readBuffer.message.reset();
-          doReadHeader();
-        }
-        else if(ec == boost::asio::error::eof || ec == boost::asio::error::connection_aborted || ec == boost::asio::error::connection_reset)
-          connectionLost();
-        else
-          connectionError("readdata", ec.message());
-      });
+            connectionError("readdata", ec.message());
+        }));
 }
 
 void Client::doWrite()
 {
   auto self(shared_from_this());
   boost::asio::async_write(m_socket, boost::asio::buffer(**m_writeQueue.front(), m_writeQueue.front()->size()),
-    [this, self](const boost::system::error_code& ec, std::size_t)
-    {
-      if(!ec)
+    m_strand.wrap(
+      [this, self](const boost::system::error_code& ec, std::size_t)
       {
-        m_writeQueue.pop();
-        if(!m_writeQueue.empty())
-          doWrite();
-      }
-      else
-        connectionError("write", ec.message());
-    });
+        if(!ec)
+        {
+          m_writeQueue.pop();
+          if(!m_writeQueue.empty())
+            doWrite();
+        }
+        else
+          connectionError("write", ec.message());
+      }));
 }
 
 void Client::processMessage(const std::shared_ptr<Message> message)
@@ -258,10 +266,14 @@ void Client::processMessage(const std::shared_ptr<Message> message)
 
 void Client::sendMessage(std::unique_ptr<Message> message)
 {
-  bool wasEmpty = m_writeQueue.empty();
-  m_writeQueue.emplace(std::move(message));
-  if(wasEmpty)
-    doWrite();
+  m_strand.post(
+    [this, msg=std::make_shared<std::unique_ptr<Message>>(std::move(message))]()
+    {
+      const bool wasEmpty = m_writeQueue.empty();
+      m_writeQueue.emplace(std::move(*msg));
+      if(wasEmpty)
+        doWrite();
+    });
 }
 
 void Client::connectionLost()
diff --git a/server/src/core/client.hpp b/server/src/core/client.hpp
index da10def1..2eb468ed 100644
--- a/server/src/core/client.hpp
+++ b/server/src/core/client.hpp
@@ -50,6 +50,7 @@ class Client : public std::enable_shared_from_this<Client>
     using ObjectHandle = uint32_t;
 
     Traintastic& m_server;
+    boost::asio::io_service::strand m_strand;
     boost::asio::ip::tcp::socket m_socket;
     const std::string m_id;
     struct
@@ -57,6 +58,7 @@ class Client : public std::enable_shared_from_this<Client>
       Message::Header header;
       std::shared_ptr<Message> message;
     } m_readBuffer;
+    std::mutex m_writeQueueMutex;
     std::queue<std::unique_ptr<Message>> m_writeQueue;
     bool m_authenticated;
     std::shared_ptr<Session> m_session;