implement basic TCP server for TMTC handling

pytmtc/tcp_server.py

@@ -0,0 +1,137 @@
+from typing import Any, Optional
+import socket
+from threading import Thread, Event, Lock
+from collections import deque
+
+from tmtccmd.com import ComInterface
+from tmtccmd.tmtc import TelemetryListT
+
+
+class TcpServer(ComInterface):
+    def __init__(self, port: int):
+        self.port = port
+        self._max_num_packets_in_tc_queue = 500
+        self._max_num_packets_in_tm_queue = 500
+        self._server_addr = ("localhost", self.port)
+        self._tc_packet_queue = deque()
+        self._tm_packet_queue = deque()
+        self._tc_lock = Lock()
+        self._tm_lock = Lock()
+        self._kill_signal = Event()
+        self._server_socket: Optional[socket.socket] = None
+        self._server_thread = Thread(target=TcpServer._server_task, daemon=True)
+        self._connected = False
+
+    @property
+    def connected(self) -> bool:
+        return self._connected
+
+    @property
+    def id(self) -> str:
+        return "tcp_server"
+
+    def initialize(self, args: Any = 0) -> Any:
+        """Perform initializations step which can not be done in constructor or which require
+        returnvalues.
+        """
+        pass
+
+    def open(self, args: Any = 0):
+        """Opens the communication interface to allow communication.
+
+        :return:
+        """
+        if self.connected:
+            return
+        self.server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        self.server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+        # We need to check the kill signal periodically to allow closing the server.
+        self.server_socket.settimeout(0.5)
+        self.server_socket.bind(self._server_addr)
+        self._connected = True
+        self._server_thread.start()
+
+    def _server_task(self):
+        assert self._server_socket is not None
+        while True and not self._kill_signal.is_set():
+            self._server_socket.listen()
+            (conn_socket, conn_addr) = self._server_socket.accept()
+            print("TCP client {} connected", conn_addr)
+            while True:
+                bytes_recvd = conn_socket.recv(4096)
+                if len(bytes_recvd) > 0:
+                    print(f"Received bytes from TCP client: {bytes_recvd.decode()}")
+                    with self._tm_lock:
+                        self._tm_packet_queue.append(bytes_recvd)
+                elif len(bytes_recvd) == 0:
+                    break
+                else:
+                    print("error receiving data from TCP client")
+
+            queue_len = 0
+            with self._tc_lock:
+                queue_len = len(self._tc_packet_queue)
+            while queue_len > 0:
+                next_packet = bytes()
+                with self._tc_lock:
+                    next_packet = self._tc_packet_queue.popleft()
+                conn_socket.sendall(next_packet)
+                queue_len -= 1
+
+    def is_open(self) -> bool:
+        """Can be used to check whether the communication interface is open. This is useful if
+        opening a COM interface takes a longer time and is non-blocking
+        """
+        return self.connected
+
+    def close(self, args: Any = 0):
+        """Closes the ComIF and releases any held resources (for example a Communication Port).
+
+        :return:
+        """
+        self._kill_signal.set()
+        self._server_thread.join()
+        self._connected = False
+
+    def send(self, data: bytes):
+        """Send raw data.
+
+        :raises SendError: Sending failed for some reason.
+        """
+        with self._tc_lock:
+            # Deque is thread-safe according to the documentation.. so this should be fine.
+            if len(self._tc_packet_queue) >= self._max_num_packets_in_tc_queue:
+                # Remove oldest packet
+                self._tc_packet_queue.popleft()
+            self._tc_packet_queue.append(data)
+
+    def receive(self, parameters: Any = 0) -> TelemetryListT:
+        """Returns a list of received packets. The child class can use a separate thread to poll for
+        the packets or use some other mechanism and container like a deque to store packets
+        to be returned here.
+
+        :param parameters:
+        :raises ReceptionDecodeError: If the underlying COM interface uses encoding and
+            decoding and the decoding fails, this exception will be returned.
+        :return:
+        """
+
+        with self._tm_lock:
+            packet_list = []
+            while self._tm_packet_queue:
+                packet_list.append(self._tm_packet_queue.popleft())
+            return packet_list
+
+    def data_available(self, timeout: float, parameters: Any = 0) -> int:
+        """Check whether TM packets are available.
+
+        :param timeout: Can be used to block on available data if supported by the specific
+            communication interface.
+        :param parameters: Can be an arbitrary parameter.
+        :raises ReceptionDecodeError: If the underlying COM interface uses encoding and
+            decoding when determining the number of available packets, this exception can be
+            thrown on decoding errors.
+        :return: 0 if no data is available, number of packets otherwise.
+        """
+        with self._tm_lock:
+            return len(self._tm_packet_queue)