Add open call as alternative to passing NetworkInterface at construction

Pros
- Allows memory to be statically allocated
- Avoids issues with Thread creation before entering main
- Matches existing APIs such as FunctionPointer and Ticker

Cons
- Does not enforce passing a NetworkInterface

Socket.cpp

@@ -16,12 +16,12 @@
 
 #include "Socket.h"
 
-Socket::Socket(NetworkInterface *iface, nsapi_protocol_t proto)
-    : _iface(iface)
+Socket::Socket()
+    : _iface(0)
+    , _socket(0)
     , _blocking(true)
     , _timeout(0)
 {
-    _socket = _iface->socket_create(proto);
 }
 
 Socket::~Socket()
@@ -31,6 +31,28 @@ Socket::~Socket()
     }
 }
 
+int Socket::open(NetworkInterface *iface, nsapi_protocol_t proto)
+{
+    _iface = iface;
+    _socket = _iface->socket_create(proto);
+}
+
+int Socket::close(bool shutdown)
+{
+    if (!_socket) {
+        return 0;
+    }
+
+    int err = _iface->socket_close(_socket, shutdown);
+    if (!err) {
+        void *socket = _socket;
+        _socket = 0;
+        _iface->socket_destroy(socket);
+    }
+
+    return err;
+}
+
 void Socket::set_blocking(bool blocking)
 {
     _blocking = blocking;
@@ -59,22 +81,6 @@ int Socket::get_option(int optname, void *optval, unsigned int *optlen)
     return _iface->socket_get_option(_socket, optname, optval, optlen);
 }
 
-int Socket::close(bool shutdown)
-{
-    if (!_socket) {
-        return 0;
-    }
-
-    int err = _iface->socket_close(_socket, shutdown);
-    if (!err) {
-        void *socket = _socket;
-        _socket = 0;
-        _iface->socket_destroy(socket);
-    }
-
-    return err;
-}
-
 void Socket::thunk(void *p) 
 {
     FunctionPointer *fptr = (FunctionPointer *)p;

Socket.h

@@ -27,6 +27,11 @@ public:
     /** Socket lifetime
      */
     virtual ~Socket();
+
+    /** Open the socket
+     *  @param iface    Interface to open socket on
+     */
+    virtual int open(NetworkInterface *iface) = 0;
     
     /** Set blocking or non-blocking mode of the socket
      *  @param blocking true for blocking mode, false for non-blocking mode.
@@ -60,7 +65,8 @@ public:
     int close(bool shutdown=true);
 
 protected:
-    Socket(NetworkInterface *iface, nsapi_protocol_t proto);
+    Socket();
+    int open(NetworkInterface *iface, nsapi_protocol_t proto);
 
     static void thunk(void *);
 

TCPServer.cpp

@@ -17,11 +17,20 @@
 #include "TCPServer.h"
 #include "Timer.h"
 
-TCPServer::TCPServer(NetworkInterface *iface)
-    : Socket(iface, NSAPI_TCP)
+TCPServer::TCPServer()
 {
 }
 
+TCPServer::TCPServer(NetworkInterface *iface)
+{
+    open(iface);
+}
+
+int TCPServer::open(NetworkInterface *iface)
+{
+    return Socket::open(iface, NSAPI_TCP);
+}
+
 int TCPServer::bind(uint16_t port)
 {
     if (!_socket) {
@@ -45,15 +54,16 @@ int TCPServer::accept(TCPSocket *connection)
     mbed::Timer timer;
     timer.start();
 
-    void *socket = connection->_socket;
-    connection->_socket = 0;
-    _iface->socket_destroy(socket);
+    if (connection->_socket) {
+        connection->close();
+    }
 
     while (true) {
         if (!_socket) {
             return NSAPI_ERROR_NO_SOCKET;   
         }
 
+        void *socket;
         int err = _iface->socket_accept(_socket, &socket);
 
         if (err > 0) {

TCPServer.h

@@ -27,8 +27,14 @@ class TCPServer : public Socket {
 public:
     /** TCP Server lifetime
      */
+    TCPServer();
     TCPServer(NetworkInterface *iface);
     virtual ~TCPServer();
+
+    /** Open the socket
+     *  @param iface    Interface to open socket on
+     */
+    virtual int open(NetworkInterface *iface);
     
     /** Bind a socket to a specific port
      * @param port      The port to listen for incoming connections on

TCPSocket.cpp

@@ -17,11 +17,20 @@
 #include "TCPSocket.h"
 #include "Timer.h"
 
-TCPSocket::TCPSocket(NetworkInterface *iface)
-    : Socket(iface, NSAPI_TCP)
+TCPSocket::TCPSocket()
 {
 }
 
+TCPSocket::TCPSocket(NetworkInterface *iface)
+{
+    open(iface);
+}
+
+int TCPSocket::open(NetworkInterface *iface)
+{
+    return Socket::open(iface, NSAPI_TCP);
+}
+
 int TCPSocket::connect(const SocketAddress &addr)
 {
     if (!_socket) {

TCPSocket.h

@@ -26,8 +26,14 @@ class TCPSocket : public Socket {
 public:
     /** TCP socket lifetime
      */
+    TCPSocket();
     TCPSocket(NetworkInterface *iface);
     virtual ~TCPSocket();
+
+    /** Open the socket
+     *  @param iface    Interface to open socket on
+     */
+    virtual int open(NetworkInterface *iface);
     
     /** Connects this TCP socket to the server
      *  @param host     The host to connect to. It can either be an IP Address

UDPSocket.cpp

@@ -17,11 +17,20 @@
 #include "UDPSocket.h"
 #include "Timer.h"
 
-UDPSocket::UDPSocket(NetworkInterface *iface)
-    : Socket(iface, NSAPI_UDP)
+UDPSocket::UDPSocket()
 {
 }
 
+UDPSocket::UDPSocket(NetworkInterface *iface)
+{
+    open(iface);
+}
+
+int UDPSocket::open(NetworkInterface *iface)
+{
+    return Socket::open(iface, NSAPI_UDP);
+}
+
 int UDPSocket::bind(uint16_t port)
 {
     if (!_socket) {

UDPSocket.h

@@ -26,8 +26,14 @@ class UDPSocket : public Socket {
 public:
     /** UDPSocket lifetime
      */
+    UDPSocket();
     UDPSocket(NetworkInterface *iface);
     virtual ~UDPSocket();
+
+    /** Open the socket
+     *  @param iface    Interface to open socket on
+     */
+    virtual int open(NetworkInterface *iface);
     
     /** Bind a UDP Server Socket to a specific port
      *  @param port     The port to listen for incoming connections on