Timeout for send and other fixes

- Socket send now has a timeout so we can eventually release the socket
  in situations where we are trying to send but the network connection
  died so there was no TCP handshake to close the connection.
- `WSGIServer` now has a 20s timeout for its sockets.
- DHCP timeout increased to 30s in accordance with RFC3315.
- Recognize more states as "socket is closed and available".
- `get_socket` now returns an invalid value if no free socket is
  available, which will cause an exception in the socket constructor.
  It used to return 0 if no sockets were available, which is a valid
  socket value, and caused all kinds of problems for the rightful
  owner of socket 0.

Author: xorbit

adafruit_wiznet5k/adafruit_wiznet5k.py

@@ -132,6 +132,7 @@
 
 # Maximum number of sockets to support, differs between chip versions.
 W5200_W5500_MAX_SOCK_NUM = const(0x08)
+SOCKET_INVALID = const(255)
 
 # UDP socket struct.
 UDP_SOCK = {"bytes_remaining": 0, "remote_ip": 0, "remote_port": 0}
@@ -163,7 +164,7 @@ def __init__(
         is_dhcp=True,
         mac=DEFAULT_MAC,
         hostname=None,
-        dhcp_timeout=3,
+        dhcp_timeout=30,
         debug=False,
     ):
         self._debug = debug
@@ -571,10 +572,16 @@ def get_socket(self):
         if self._debug:
             print("*** Get socket")
 
-        sock = 0
+        sock = SOCKET_INVALID
         for _sock in range(self.max_sockets):
             status = self.socket_status(_sock)[0]
-            if status in (SNSR_SOCK_CLOSED, SNSR_SOCK_FIN_WAIT, SNSR_SOCK_CLOSE_WAIT):
+            if status in (
+                SNSR_SOCK_CLOSED,
+                SNSR_SOCK_TIME_WAIT,
+                SNSR_SOCK_FIN_WAIT,
+                SNSR_SOCK_CLOSE_WAIT,
+                SNSR_SOCK_CLOSING,
+            ):
                 sock = _sock
                 break
 
@@ -616,7 +623,13 @@ def socket_open(self, socket_num, conn_mode=SNMR_TCP):
         if self._debug:
             print("*** Opening socket %d" % socket_num)
         status = self._read_snsr(socket_num)[0]
-        if status in (SNSR_SOCK_CLOSED, SNSR_SOCK_FIN_WAIT, SNSR_SOCK_CLOSE_WAIT):
+        if status in (
+            SNSR_SOCK_CLOSED,
+            SNSR_SOCK_TIME_WAIT,
+            SNSR_SOCK_FIN_WAIT,
+            SNSR_SOCK_CLOSE_WAIT,
+            SNSR_SOCK_CLOSING,
+        ):
             if self._debug:
                 print("* Opening W5k Socket, protocol={}".format(conn_mode))
             time.sleep(0.00025)
@@ -714,7 +727,7 @@ def read_udp(self, socket_num, length):
             return ret, resp
         return -1
 
-    def socket_write(self, socket_num, buffer):
+    def socket_write(self, socket_num, buffer, timeout=0):
         """Writes a bytearray to a provided socket."""
         assert self.link_status, "Ethernet cable disconnected!"
         assert socket_num <= self.max_sockets, "Provided socket exceeds max_sockets."
@@ -725,13 +738,16 @@ def socket_write(self, socket_num, buffer):
             ret = SOCK_SIZE
         else:
             ret = len(buffer)
+        stamp = time.monotonic()
 
         # if buffer is available, start the transfer
         free_size = self._get_tx_free_size(socket_num)
         while free_size < ret:
             free_size = self._get_tx_free_size(socket_num)
             status = self.socket_status(socket_num)[0]
-            if status not in (SNSR_SOCK_ESTABLISHED, SNSR_SOCK_CLOSE_WAIT):
+            if status not in (SNSR_SOCK_ESTABLISHED, SNSR_SOCK_CLOSE_WAIT) or (
+                timeout and time.monotonic() - stamp > timeout
+            ):
                 ret = 0
                 break
 
@@ -756,9 +772,11 @@ def socket_write(self, socket_num, buffer):
         ) != SNIR_SEND_OK:
             if self.socket_status(socket_num)[0] in (
                 SNSR_SOCK_CLOSED,
+                SNSR_SOCK_TIME_WAIT,
                 SNSR_SOCK_FIN_WAIT,
                 SNSR_SOCK_CLOSE_WAIT,
-            ):
+                SNSR_SOCK_CLOSING,
+            ) or (timeout and time.monotonic() - stamp > timeout):
                 # self.socket_close(socket_num)
                 return 0
             time.sleep(0.01)

adafruit_wiznet5k/adafruit_wiznet5k_dhcp.py

@@ -101,7 +101,7 @@ class DHCP:
 
     # pylint: disable=too-many-arguments, too-many-instance-attributes, invalid-name
     def __init__(
-        self, eth, mac_address, hostname=None, response_timeout=5, debug=False
+        self, eth, mac_address, hostname=None, response_timeout=30, debug=False
     ):
         self._debug = debug
         self._response_timeout = response_timeout

adafruit_wiznet5k/adafruit_wiznet5k_socket.py

@@ -63,7 +63,7 @@ def htons(x):
 TCP_MODE = 80
 SOCK_DGRAM = const(0x02)  # UDP
 AF_INET = const(3)
-NO_SOCKET_AVAIL = const(255)
+SOCKET_INVALID = const(255)
 
 
 # pylint: disable=too-many-arguments, unused-argument
@@ -123,6 +123,8 @@ def __init__(
         self._listen_port = None
 
         self._socknum = _the_interface.get_socket()
+        if self._socknum == SOCKET_INVALID:
+            raise RuntimeError("Failed to allocate socket.")
 
     @property
     def socknum(self):
@@ -201,7 +203,7 @@ def send(self, data):
         :param bytearray data: Desired data to send to the socket.
 
         """
-        _the_interface.socket_write(self.socknum, data)
+        _the_interface.socket_write(self.socknum, data, self._timeout)
         gc.collect()
 
     def recv(self, bufsize=0):  # pylint: disable=too-many-branches

adafruit_wiznet5k/adafruit_wiznet5k_wsgiserver.py

@@ -43,8 +43,8 @@ def set_interface(iface):
     socket.set_interface(iface)
 
 
-# Maximum number of sockets for the web server, leave one for other things
-MAX_SOCK_NUM = const(7)
+# Maximum number of sockets for the web server (number of connections we can hold)
+MAX_SOCK_NUM = const(6)
 
 # pylint: disable=invalid-name
 class WSGIServer:
@@ -55,6 +55,7 @@ class WSGIServer:
     def __init__(self, port=80, debug=False, application=None):
         self.application = application
         self.port = port
+        self._timeout = 20
         self._client_sock = []
         self._debug = debug
 
@@ -69,6 +70,7 @@ def start(self):
         """
         for _ in range(MAX_SOCK_NUM):
             new_sock = socket.socket()
+            new_sock.settimeout(self._timeout)
             new_sock.bind((None, self.port))
             new_sock.listen()
             self._client_sock.append(new_sock)
@@ -90,6 +92,7 @@ def update_poll(self):
                 self.finish_response(result, sock)
                 self._client_sock.remove(sock)
                 new_sock = socket.socket()
+                new_sock.settimeout(self._timeout)
                 new_sock.bind((None, self.port))
                 new_sock.listen()
                 add_sock.append(new_sock)