diff --git a/Release/Duet-0.6-0.8.5/Edge/iap.bin b/Release/Duet-0.6-0.8.5/Edge/iap.bin
new file mode 100644
index 0000000..0ccbce6
Binary files /dev/null and b/Release/Duet-0.6-0.8.5/Edge/iap.bin differ
diff --git a/Release/Duet-Ethernet/Edge/DuetEthernetFirmware-1.18beta1.bin b/Release/Duet-Ethernet/Edge/DuetEthernetFirmware-1.18beta1.bin
new file mode 100644
index 0000000..8ab9236
Binary files /dev/null and b/Release/Duet-Ethernet/Edge/DuetEthernetFirmware-1.18beta1.bin differ
diff --git a/Release/Duet-Ethernet/Edge/iap4e.bin b/Release/Duet-Ethernet/Edge/iap4e.bin
new file mode 100644
index 0000000..9e82953
Binary files /dev/null and b/Release/Duet-Ethernet/Edge/iap4e.bin differ
diff --git a/Release/Duet-WiFi/Edge/iap4e.bin b/Release/Duet-WiFi/Edge/iap4e.bin
new file mode 100644
index 0000000..9e82953
Binary files /dev/null and b/Release/Duet-WiFi/Edge/iap4e.bin differ
diff --git a/src/DuetNG/DuetEthernet/Network.cpp b/src/DuetNG/DuetEthernet/Network.cpp
index 863330d..4bb45f3 100644
--- a/src/DuetNG/DuetEthernet/Network.cpp
+++ b/src/DuetNG/DuetEthernet/Network.cpp
@@ -8,6 +8,7 @@
 #include "Network.h"
 #include "NetworkTransaction.h"
 #include "Platform.h"
+#include "RepRap.h"
 #include "wizchip_conf.h"
 #include "Wiznet/Internet/DHCP/dhcp.h"
 
@@ -356,6 +357,10 @@ bool Network::AcquireTransaction(size_t socketNumber)
 	{
 		currentTransactionSocketNumber = socketNumber;
 	}
+	else if (reprap.Debug(moduleNetwork))
+	{
+		debugPrintf("Failed to acquire transaction for socket %u\n", socketNumber);
+	}
 	return success;
 }
 
@@ -381,7 +386,7 @@ void Network::TerminateSockets()
 
 void Network::Defer(NetworkTransaction *tr)
 {
-	const Socket *skt = tr->GetConnection();
+	const Socket * const skt = tr->GetConnection();
 	if (skt != nullptr && skt->GetNumber() == currentTransactionSocketNumber)
 	{
 		++currentTransactionSocketNumber;
diff --git a/src/DuetNG/DuetEthernet/Network.h b/src/DuetNG/DuetEthernet/Network.h
index ef51dc7..7a84749 100644
--- a/src/DuetNG/DuetEthernet/Network.h
+++ b/src/DuetNG/DuetEthernet/Network.h
@@ -81,18 +81,20 @@ public:
 private:
 	enum class NetworkState
 	{
-		disabled,					// WiFi not active
-		enabled,					// WiFi enabled but not started yet
-		establishingLink,			// starting up (waiting for initialisation)
-		obtainingIP,
-		active
+		disabled,					// Network disabled
+		enabled,					// Network enabled but not started yet
+		establishingLink,			// starting up, waiting for link
+		obtainingIP,				// link established, waiting for DHCP
+		active						// network running
 	};
 
 	void InitSockets();
 	void TerminateSockets();
-	bool AcquireTransaction(size_t socketNumber);
 
-	Platform *platform;
+	bool AcquireTransaction(size_t socketNumber)
+	pre(socketNumber < NumTcpSockets);
+
+	Platform * const platform;
 	float longWait;
 	uint32_t lastTickMillis;
 
diff --git a/src/DuetNG/DuetEthernet/Socket.cpp b/src/DuetNG/DuetEthernet/Socket.cpp
index dcd281c..b39b4c7 100644
--- a/src/DuetNG/DuetEthernet/Socket.cpp
+++ b/src/DuetNG/DuetEthernet/Socket.cpp
@@ -17,8 +17,6 @@
 //***************************************************************************************************
 // Socket class
 
-#define IMMEDIATE_ACQUIRE	1
-
 Socket::Socket() : currentTransaction(nullptr), receivedData(nullptr), state(SocketState::inactive)
 {
 }
@@ -43,7 +41,6 @@ void Socket::ReInit()
 	persistConnection = true;
 	isTerminated = false;
 	isSending = false;
-	needTransaction = false;
 	state = SocketState::inactive;
 
 	// Re-initialise the socket on the W5500
@@ -187,8 +184,7 @@ void Socket::Poll(bool full)
 
 		if (state == SocketState::listening)		// if it is a new connection
 		{
-			needTransaction = false;
-			if (socketNum == FtpSocketNumber || socketNum == TelnetSocketNumber)
+			if (socketNum == FtpSocketNumber || socketNum == FtpDataSocketNumber || socketNum == TelnetSocketNumber)
 			{
 				// FTP and Telnet protocols need a connection reply, so tell the Webserver module about the new connection
 				if (currentTransaction == nullptr)
@@ -229,7 +225,6 @@ void Socket::Poll(bool full)
 			}
 		}
 
-#ifdef IMMEDIATE_ACQUIRE
 		if (currentTransaction == nullptr && receivedData != nullptr)
 		{
 			currentTransaction = NetworkTransaction::Allocate();
@@ -238,17 +233,6 @@ void Socket::Poll(bool full)
 				currentTransaction->Set(this, TransactionStatus::receiving);
 			}
 		}
-#else
-		if (currentTransaction == nullptr && (receivedData != nullptr || needTransaction))
-		{
-			currentTransaction = NetworkTransaction::Allocate();
-			if (currentTransaction != nullptr)
-			{
-				currentTransaction->Set(this, (needTransaction) ? TransactionStatus::acquired : TransactionStatus::receiving);
-				needTransaction = false;
-			}
-		}
-#endif
 
 		// See if we can send any data.
 		// Currently we don't send if we are being called from hsmci because we don't want to risk releasing a buffer that we may be reading data into.
@@ -298,27 +282,16 @@ void Socket::Poll(bool full)
 		break;
 
 	case SOCK_CLOSED:
-#ifdef _HTTPSERVER_DEBUG_
-		printf("> HTTPSocket[%d] : CLOSED\r\n", s);
-#endif
-		reprap.GetWebserver()->ConnectionLost(this);						// the webserver needs this to be called for both graceful and disgraceful disconnects
-		state = SocketState::inactive;
-
-		if (socket(socketNum, Sn_MR_TCP, localPort, 0x00) == socketNum)		// Reinitialize the socket
+		if (full)									// don't make a call to webserver if we might be in it already
 		{
-#ifdef _HTTPSERVER_DEBUG_
-			printf("> HTTPSocket[%d] : OPEN\r\n", socketNum);
-#endif
+			reprap.GetWebserver()->ConnectionLost(this);	// the webserver needs this to be called for both graceful and disgraceful disconnects
+			ReInit();
 		}
 		break;
 
 	default:
 		break;
-	} // end of switch
-
-#ifdef _USE_WATCHDOG_
-	HTTPServer_WDT_Reset();
-#endif
+	}
 }
 
 // Try to send data, returning true if all data has been sent and we ought to close the socket
@@ -333,7 +306,7 @@ bool Socket::TrySendData()
 			setSn_IR(socketNum, Sn_IR_SENDOK);		// if yes
 			isSending = false;
 		}
-		else if(tmp & Sn_IR_TIMEOUT)				// did it time out?
+		else if (tmp & Sn_IR_TIMEOUT)				// did it time out?
 		{
 			isSending = false;
 			disconnectNoWait(socketNum);			// if so, close the socket
@@ -406,17 +379,12 @@ bool Socket::AcquireTransaction()
 
 	if (getSn_SR(socketNum) == SOCK_ESTABLISHED)
 	{
-#ifdef IMMEDIATE_ACQUIRE
 		currentTransaction = NetworkTransaction::Allocate();
 		if (currentTransaction != nullptr)
 		{
 			currentTransaction->Set(this, TransactionStatus::acquired);
 			return true;
 		}
-#else
-		needTransaction = true;
-		return true;
-#endif
 	}
 	return false;
 }
diff --git a/src/DuetNG/DuetEthernet/Socket.h b/src/DuetNG/DuetEthernet/Socket.h
index c37a4e8..96154a5 100644
--- a/src/DuetNG/DuetEthernet/Socket.h
+++ b/src/DuetNG/DuetEthernet/Socket.h
@@ -61,7 +61,6 @@ private:
 	SocketNumber socketNum;								// The W5500 socket number we are using
 	SocketState state;
 	bool isSending;										// True if we have written data to the W5500 to send and have not yet seen success or timeout
-	bool needTransaction;								// True if the web server has asked for a transaction
 };
 
 #endif /* SRC_DUETNG_DUETETHERNET_SOCKET_H_ */
diff --git a/src/DuetNG/DuetEthernet/Webserver.cpp b/src/DuetNG/DuetEthernet/Webserver.cpp
index 20c8c1e..fa11a56 100644
--- a/src/DuetNG/DuetEthernet/Webserver.cpp
+++ b/src/DuetNG/DuetEthernet/Webserver.cpp
@@ -1955,7 +1955,7 @@ void Webserver::FtpInterpreter::ConnectionEstablished()
 	}
 
 	// Is this a new connection on the data port?
-	NetworkTransaction *transaction = webserver->currentTransaction;
+	NetworkTransaction * const transaction = webserver->currentTransaction;
 	if (transaction->GetLocalPort() != FTP_PORT)
 	{
 		if (state == waitingForPasvPort)
@@ -2343,7 +2343,7 @@ void Webserver::FtpInterpreter::ProcessLine()
 					SendReply(150, "Here comes the directory listing.");
 
 					// send directory listing via data port
-					NetworkTransaction *dataTransaction = network->GetTransaction();
+					NetworkTransaction * const dataTransaction = network->GetTransaction();
 
 					FileInfo fileInfo;
 					if (platform->GetMassStorage()->FindFirst(currentDir, fileInfo))
diff --git a/src/DuetNG/DuetEthernet/Wiznet/Ethernet/WizSpi.cpp b/src/DuetNG/DuetEthernet/Wiznet/Ethernet/WizSpi.cpp
index c11f41a..a633046 100644
--- a/src/DuetNG/DuetEthernet/Wiznet/Ethernet/WizSpi.cpp
+++ b/src/DuetNG/DuetEthernet/Wiznet/Ethernet/WizSpi.cpp
@@ -25,7 +25,7 @@
 #include "matrix.h"
 
 // Functions called by the W5500 module to transfer data to/from the W5500 via SPI
-const uint32_t SpiClockFrequency = 60000000;
+const uint32_t SpiClockFrequency = 40000000;			// tried 60MHz and we got some data corruption when uploading files, so try 40MHz instead
 const unsigned int SpiPeripheralChannelId = 0;			// we use NPCS0 as the slave select signal
 
 #if USE_PDC
diff --git a/src/Movement/Move.cpp b/src/Movement/Move.cpp
index c3d74d9..1e53584 100644
--- a/src/Movement/Move.cpp
+++ b/src/Movement/Move.cpp
@@ -1063,7 +1063,7 @@ void Move::DoDeltaCalibration(size_t numFactors, StringRef& reply)
 	// Transform the probing points to motor endpoints and store them in a matrix, so that we can do multiple iterations using the same data
 	FixedMatrix<floatc_t, MaxDeltaCalibrationPoints, DELTA_AXES> probeMotorPositions;
 	floatc_t corrections[MaxDeltaCalibrationPoints];
-	float_t initialSumOfSquares = 0.0;
+	float initialSumOfSquares = 0.0;
 	for (size_t i = 0; i < numPoints; ++i)
 	{
 		corrections[i] = 0.0;
diff --git a/src/Version.h b/src/Version.h
index 03326bb..bd24077 100644
--- a/src/Version.h
+++ b/src/Version.h
@@ -13,7 +13,7 @@
 #endif
 
 #ifndef DATE
-# define DATE "2017-02-21"
+# define DATE "2017-02-24"
 #endif
 
 #define AUTHORS "reprappro, dc42, chrishamm, t3p3, dnewman"