Added multi option to Server class.

Activating this option tells a server instance to accept multiple
client connections. Not activating it, which is the default, maintains
the established behavior, where the server would shut down as soon as
the first connected client disconnects itself.

deploy/coverage.py

@@ -18,7 +18,7 @@
 from pathlib import Path
 
 tests = ['meta', 'config', 'discovery', 'server', 'session', 'standalone',
-         'client', 'node', 'model', 'exit']
+         'client', 'multi', 'node', 'model', 'exit']
 
 here = Path(__file__).resolve().parent
 root = here.parent

deploy/test.py

@@ -17,7 +17,7 @@
 import sys
 
 tests = ['meta', 'config', 'discovery', 'server', 'session', 'standalone',
-         'client', 'node', 'model', 'exit']
+         'client', 'multi', 'node', 'model', 'exit']
 
 folder = Path(__file__).parent.parent / 'tests'
 python = sys.executable

mph/client.py

@@ -354,8 +354,8 @@ def disconnect(self):
         """
         Disconnects the client from the server.
 
-        Note that the server, unless started with the command-line option
-        `-multi on`, will shut down when the client disconnects.
+        Note that the server, unless started with the option `multi`
+        set to `'on'`, will shut down as soon as the client disconnects.
         """
         if self.port:
             log.debug('Disconnecting from server.')

mph/server.py

@@ -14,7 +14,6 @@
 from subprocess import TimeoutExpired  # communication time-out
 from re import match as regex          # regular expression
 from time import perf_counter as now   # wall-clock time
-from sys import version_info           # Python version
 from logging import getLogger          # event logging
 
 ########################################
@@ -61,12 +60,18 @@ class Server:
     server will then select a random free port, which will almost always
     avoid collisions.
 
+    If `multi` is `False` or `'off'` or `None` (the default), then
+    the server will shut down as soon as the first connected clients
+    disconnects itself. If it is `True` or `'on'`, the server process
+    will stay alive and accept multiple client connections.
+
     A `timeout` can be set for the server start-up. The default is 60
     seconds. `TimeoutError` is raised if the server failed to start
     within that period.
     """
 
-    def __init__(self, cores=None, version=None, port=None, timeout=60):
+    def __init__(self, cores=None, version=None, port=None,
+                       multi=None, timeout=60):
 
         # Start Comsol server as an external process.
         backend = discovery.backend(version)
@@ -81,9 +86,17 @@ def __init__(self, cores=None, version=None, port=None, timeout=60):
             log.info(f'Server restricted to {cores} processor {noun}.')
         if port is not None:
             arguments += ['-port', str(port)]
+        if multi:
+            if multi in (True, 'on'):
+                arguments += ['-multi', 'on']
+            elif multi in (False, 'off'):
+                arguments += ['-multi', 'off']
+            else:
+                error = f'Invalid value "{multi}" for option "multi".'
+                log.error(error)
+                raise ValueError(error)
         command = server + arguments
-        if version_info < (3, 8):
-            command[0] = str(command[0])
+        command[0] = str(command[0])   # Required for Python 3.6 and 3.7.
         process = start(command, stdin=PIPE, stdout=PIPE, errors='ignore')
 
         # Remember the requested port (if any).

tests/test_multi.py

@@ -0,0 +1,74 @@
+"""Tests multiple client connections to the same server."""
+
+########################################
+# Dependencies                         #
+########################################
+import parent # noqa F401
+import mph
+from sys import argv
+from time import sleep
+from pytest import raises
+import logging
+
+
+########################################
+# Fixtures                             #
+########################################
+server = None
+
+
+def teardown_module():
+    if server and server.running():
+        try:
+            server.stop()
+        except Exception:
+            pass
+
+
+########################################
+# Tests                                #
+########################################
+
+def test_multi():
+    global server
+    with raises(ValueError):
+        server = mph.Server(multi='invalid')
+    server = mph.Server(cores=1, multi=False)
+    assert server.running()
+    assert server.port
+    client = mph.Client(port=server.port)
+    assert not client.standalone
+    assert client.version == server.version
+    assert client.cores == server.cores
+    assert client.port == server.port
+    client.disconnect()
+    sleep(3)
+    assert not server.running()
+    server = mph.Server(cores=1, multi=True)
+    client.connect(port=server.port)
+    assert client.version == server.version
+    assert client.cores == server.cores
+    assert client.port == server.port
+    client.disconnect()
+    sleep(3)
+    assert server.running()
+    server.stop()
+
+
+########################################
+# Main                                 #
+########################################
+
+if __name__ == '__main__':
+
+    arguments = argv[1:]
+    if 'log' in arguments:
+        logging.basicConfig(
+            level   = logging.DEBUG if 'debug' in arguments else logging.INFO,
+            format  = '[%(asctime)s.%(msecs)03d] %(message)s',
+            datefmt = '%H:%M:%S')
+
+    try:
+        test_multi()
+    finally:
+        teardown_module()