diff --git a/feeder.py b/feeder.py
index 95e47ed..928fc5d 100644
--- a/feeder.py
+++ b/feeder.py
@@ -1,6 +1,7 @@
+import sys
 from streams import EventStream
 from nicoscache import NicosStream
-from secop import ScanStream, ScanReply
+from secop import ScanStream, ScanReply, send_fake_udp
 from influx import testdb
 
 
@@ -20,4 +21,7 @@ def main():
         db.disconnect()
 
 
-main()
+if len(sys.argv) > 1:
+    send_fake_udp(*sys.argv[1:])
+else:
+    main()
diff --git a/influx.py b/influx.py
index d80f3e6..69c51c6 100644
--- a/influx.py
+++ b/influx.py
@@ -105,6 +105,30 @@ class NamedTuple(tuple):
                 raise
             return default
 
+    @property
+    def names(self):
+        return tuple(self._idx_by_name)
+
+    def tuple(self, *keys):
+        return tuple(self.get(k) for k in keys)
+
+
+class Table(list):
+    """a list of tuples with meta info"""
+    def __init__(self, tags, key_names, column_names):
+        super().__init__()
+        self.tags = tags
+        self.key_names = key_names
+        self.column_names = column_names
+
+
+class Single(Table):
+    """a single row of a table, as a list with meta info"""
+    def __init__(self, table):
+        super().__init__(table.tags, table.key_names, table.column_names)
+        single, = table
+        self[:] = single
+
 
 class RegExp(str):
     """indicates, tht this string should be treated as regexp
@@ -229,23 +253,28 @@ class InfluxDBWrapper:
 
     # query the database
 
-    def query(self, start=None, stop=None, interval=None, last=False, columns=None, **tags):
+    def query(self, start=None, stop=None, interval=None, single=None, columns=None, **tags):
         """Returns queried data as InfluxDB tables
 
         :param start: start time. default is a month ago
         :param stop: end time, default is tomorrow at the same time
         :param interval: if set an aggregation filter will be applied. This will
                          return only the latest values per time interval in seconds.
-        :param last: when True, only the last value within the interval is returned
-                     (for any existing combinations of tags!)
+        :param single: when True (or 1), only the last value within the interval is returned
+                       (for any existing combinations of tags!)
+                       single=-1: return the first value instead
         :param columns: if given, return only these columns (in addition to '_time' and '_value')
         :param tags: selection criteria:
              <tag>=None
-                 return records independent of this tag. the value will be contained in the result dicts key
+                 return records independent of this tag.
+                 the obtained value will be contained in the result dicts key
              <tag>=[<value1>, <value2>, ...]
-                 return records where tag is one from the list. the value is contained in the result dicts key
-             <tag>>=<value>:
-                 return only records with given tag matching <value>. the value is not part of the results key
+                 return records where tag is one from the list.
+                 the obtained value is contained in the result dicts key
+             <tag>=<value>:
+                 return only records with given tag matching <value>.
+                 the obtained value is contained in the result dicts key only
+                 if the value is an instance of RegExp or when it contains an asterisk ('*')
 
         :return: a dict <tuple of key values> of list of <row>
              where <tuple of keys> and <row> are NamedTuple
@@ -255,55 +284,61 @@ class InfluxDBWrapper:
         msg = [f'from(bucket:"{self._bucket}")',
                f'|> range(start: {start}, stop: {stop})']
 
-        keynames = []
+        keys = {}
         dropcols = ['_start', '_stop']
+        fixed_tags = {}
         for key, crit in tags.items():
             if crit is None:
-                keynames.append(key)
+                keys[key] = None
                 continue
             if isinstance(crit, str):
                 if isinstance(crit, RegExp) or '*' in crit:
-                    keynames.append(key)
+                    keys[key] = None
                     append_wildcard_filter(msg, key, [crit])
                     continue
+                fixed_tags[key] = crit
                 dropcols.append(key)
                 crit = f'"{crit}"'
             elif isinstance(crit, (int, float)):
+                fixed_tags[key] = crit
                 dropcols.append(key)
             else:
                 try:
-                    keynames.append(key)
+                    keys[key] = None
                     append_wildcard_filter(msg, key, crit)
                     continue
                 except Exception:
                     raise ValueError(f'illegal value for {key}: {crit}')
             msg.append(f'|> filter(fn:(r) => r.{key} == {crit})')
-        if last:
-            msg.append('|> last(column: "_time")')
+        if single:
+            if single < 0:
+                msg.append('|> first(column: "_time")')
+            else:
+                msg.append('|> last(column: "_time")')
         if interval:
             msg.append(f'|> aggregateWindow(every: {interval}s, fn: last, createEmpty: false)')
         if columns is None:
             msg.append(f'''|> drop(columns:["{'","'.join(dropcols)}"])''')
         else:
             columns = ['_time', '_value'] + list(columns)
-            msg.append(f'''|> keep(columns:["{'","'.join(columns + keynames)}"])''')
+            msg.append(f'''|> keep(columns:["{'","'.join(columns + keys)}"])''')
 
         msg = '\n'.join(msg)
         print(msg)
 
         reader = self._client.query_api().query_csv(msg)
-        print('CSV')
+        print('CSV', keys, columns)
         converters = None
         group = None
         column_names = None
+        column_keys = None
         key = None
         result = {}
-        table = None
+        tableno = None
 
         for row in reader:
             if not row:
                 continue
-            print(row)
             if row[0]:
                 if row[0] == '#datatype':
                     converters = {i: CONVERTER.get(d) for i, d in enumerate(row) if i > 2}
@@ -312,31 +347,27 @@ class InfluxDBWrapper:
                     group = row
                 continue
             if column_names is None:
-                print('COL', row)
                 column_names = row
-                keys = {}
                 for col, (name, grp) in enumerate(zip(column_names, group)):
                     if grp != 'true':
                         continue
-                    # if name in keynames or (columns is None and name not in dropcols):
-                    if name in keynames or columns is None:
-                        keys[col] = converters.pop(col)
-                valuecls = NamedTuple([row[i] for i in converters])
-                keycls = NamedTuple([row[i] for i in keys])
+                    if columns is None or name in keys:
+                        keys[name] = col, converters.pop(col)
+                column_keys = tuple(column_names[i] for i in converters)
                 continue
-            if row[2] != table:
+            if row[2] != tableno:
                 # new table, new key
-                table = row[2]
-                key = keycls(f(row[i]) for i, f in keys.items())
-                print('new table', table, key)
+                tableno = row[2]
+                key_dict = {n: f(row[i]) for n, (i, f) in keys.items()}
+                key = tuple(key_dict.values())
                 if result.get(key) is None:
-                    result[key] = []
+                    print('KC', key_dict, column_keys)
+                    result[key] = Table({**fixed_tags, **key_dict}, tuple(keys), column_keys)
 
-            result[key].append(valuecls(f(row[i]) for i, f in converters.items()))
-        if last:
-            print('LAST')
+            result[key].append(tuple(f(row[i]) for i, f in converters.items()))
+        if single:
             for key, table in result.items():
-                result[key], = table
+                result[key] = Single(table)
         else:
             for table in result.values():
                 table.sort()
@@ -354,9 +385,10 @@ class InfluxDBWrapper:
         :param add_prev: amount of time to look back for the last previous point (default: 1 hr)
         :param add_end: whether to add endpoint at stop time (default: False)
         :param tags: further selection criteria
-        :return: a dict <tuple of key values> of list of <row>
-             where <tuple of keys> and <row> are NamedTuple
-             <row> is (<timestamp>, <value>)
+        :return: a dict <tuple of key values> of <Table> or <Single>
+
+        where <Table> is a list of tuples with some meta info (table.tags, table.column_names)
+        and <Single> is a list (a single row of a table) with the same meta info
 
         when _field='float' (the default), the returned values are either a floats or None
         """
@@ -370,7 +402,7 @@ class InfluxDBWrapper:
         else:
             result = {}
         if add_prev:
-            prev_data = self.query(rstart - add_prev, rstart, last=True, **tags)
+            prev_data = self.query(rstart - add_prev, rstart, single=1, **tags)
             for key, first in prev_data.items():
                 curve = result.get(key)
                 if first[1] is not None:
diff --git a/secop.py b/secop.py
index fde46ee..4f85ec4 100644
--- a/secop.py
+++ b/secop.py
@@ -110,9 +110,12 @@ class UdpStream(Base):
             except socket.error:  # pragma: no cover
                 return None
             msg = json.loads(msg.decode('utf-8'))
-            if msg['SECoP'] != 'node':
+            if msg['SECoP'] == 'for_other_node':
+                uri = msg['uri']
+            elif msg['SECoP'] == 'node':
+                uri = f"{addr[0]}:{msg['port']}"
+            else:
                 continue
-            uri = f"{addr[0]}:{msg['port']}"
             yield SecopStream, uri, msg['equipment_id']
 
 
@@ -144,5 +147,14 @@ class ScanStream(UdpStream):
         self.select_dict[sock.fileno()] = self
 
 
+def send_fake_udp(uri, equipment_id='fake'):
+    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+    sock.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
+    msg = json.dumps({
+        'SECoP': 'for_other_node',
+        'uri': uri,
+        'equipment_id': equipment_id,
+    }, ensure_ascii=False, separators=(',', ':')).encode('utf-8')
+    sock.sendto(msg, ('255.255.255.255', SECOP_UDP_PORT))
 
 
diff --git a/t.py b/t.py
index a96d0cf..6b46093 100644
--- a/t.py
+++ b/t.py
@@ -46,3 +46,31 @@ def crv(*args, **kwds):
     global result
     result = db.curves(*args, **kwds)
     prt()
+
+
+def sry():
+    global result
+    res = db.query(-DAY * 365, interval=DAY, _field='float',
+                   device=None, stream=None, _measurement=None)
+    result = {}  # dict (device, stream) of list of [start, end, set of params]
+    for key, table in res.items():
+        assert table.key_names == ('device', 'stream', '_measurement')
+        device, stream, param = key
+        for row in table:
+            start = row[0] - 3600
+            result.setdefault((start, device, stream), set()).add(param)
+    prev_data = {}
+    summary = []
+    for (start, device, stream), pset in sorted(result.items()):
+        prev = prev_data.get((device, stream))
+        if prev is None or start > prev[1]:
+            if prev:
+                print('PREV', device, stream, start - prev[1])
+            prev_data[device, stream] = prev = [start, start + 3600, pset]
+            summary.append([start, device, stream, prev])
+        else:
+            prev[1] = start + 3600
+            prev[2].update(pset)
+    for start, device, stream, (_, end, pset) in sorted(summary):
+        st = time.strftime('%Y-%m-%d %H:%M', time.localtime(start))
+        print(st, (end - start) / 3600., device, stream, len(pset))