HTTP/VistA protocol switcher & debugger

main.py

@@ -9,6 +9,7 @@ from flask.json.provider import DefaultJSONProvider
 
 import rpc
 import util
+import protoswitch
 
 import logging
 
@@ -159,4 +160,4 @@ if __name__ == '__main__':
 	port = get_port()
 	print(f'http://localhost:{port}/#{app.secret}')
 	webbrowser.open(f'http://localhost:{port}/#{app.secret}')
-	app.run(port=port)
+	app.run(port=port, request_handler=protoswitch.SwitchingRequestHandler)

protoswitch.py

@@ -0,0 +1,71 @@
+#!/usr/bin/env python3
+
+import socket
+import io
+from werkzeug.serving import WSGIRequestHandler
+
+from typing import Iterator
+
+import logging
+
+logger = logging.getLogger(__name__)
+handler = logging.StreamHandler()
+handler.setFormatter(logging.Formatter('%(asctime)s:%(levelname)s\t%(message)s'))
+logger.addHandler(handler)
+logger.setLevel(logging.DEBUG)
+
+bEOT = b'\x04'
+
+class SwitchingRequestHandler(WSGIRequestHandler):
+	def parse_request(self):
+		if self.raw_requestline.startswith(b'[XWB]'):
+			logger.info(f"{self.client_address[0]}:{self.client_address[1]} VistA OPEN")
+			proxy_vista(read_from_file(self.rfile, self.raw_requestline), self.wfile, self.client_address, ('test.northport.med.va.gov', 19009))
+			logger.info(f"{self.client_address[0]}:{self.client_address[1]} VistA CLOSE")
+			return False
+		return WSGIRequestHandler.parse_request(self)
+
+def proxy_vista(rfilegen: Iterator[bytes], wfile: io.BufferedWriter, localaddr: tuple, remoteaddr: tuple) -> None:
+	remotesock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+	remotesock.connect(remoteaddr)
+	recipient = recv_from_socket(remotesock)
+	for n, req in enumerate(rfilegen):
+		logger.debug(f"{localaddr[0]}:{localaddr[1]} #{n} → {req.decode('latin-1').encode('unicode-escape').decode()}")
+		remotesock.send(req + bEOT)
+		res = next(recipient)
+		for line in res.decode('latin-1').splitlines(keepends=True):
+			logger.debug(f"{localaddr[0]}:{localaddr[1]} #{n} ← {line.encode('unicode-escape').decode()}")
+		wfile.write(res + bEOT)
+	remotesock.shutdown(socket.SHUT_RDWR)
+	remotesock.close()
+
+def read_from_file(rfile: io.BufferedReader, buf: bytes=b'', end: bytes=bEOT, minsz: int=1024, maxsz: int=32768) -> Iterator[bytes]:
+	if len(buf) > 0:
+		while (idx := buf.find(end)) >= 0:
+			if idx > 0:
+				yield buf[:idx]
+			buf = buf[idx + 1:]
+	bufsz = minsz
+	while len(data := rfile.read1(bufsz)) > 0:
+		buf += data
+		while (idx := buf.find(end)) >= 0:
+			if idx > 0:
+				yield buf[:idx]
+				bufsz = minsz
+			elif bufsz < maxsz:
+				bufsz = _x if (_x := bufsz << 1) < maxsz else maxsz
+			buf = buf[idx + 1:]
+
+def recv_from_socket(sock: socket.socket, end: bytes=bEOT, minsz: int=1024, maxsz: int=32768) -> Iterator[bytes]:
+	buf = b''
+	bufsz = minsz
+	while True:
+		if len(data := sock.recv(bufsz)) > 0:
+			buf += data
+			while (idx := buf.find(end)) >= 0:
+				if idx > 0:
+					yield buf[:idx]
+					bufsz = minsz
+				elif bufsz < maxsz:
+					bufsz = _x if (_x := bufsz << 1) < maxsz else maxsz
+				buf = buf[idx + 1:]