excessive connection retries on bad electrums

[cipig]

i stumbled upon one electrum server which shows this when i pass a manual request:

(echo '{ "id": 1, "method": "server.version", "params": ["barterDEX", ["1.4", "2.0"]] }'; sleep 0.5) | ncat --ssl zeta-seed-c.zetacoin.tech 50012

HTTP/1.1 400 Bad Request
Date: Tue, 07 Dec 2021 09:10:09 GMT
Server: Python/3.7 websockets/10.1
Content-Length: 77
Content-Type: text/plain
Connection: close

Failed to open a WebSocket connection: did not receive a valid HTTP request.

problem is that mm2 tries like crazy to reconnect to it, this i a sequence:

07 09:06:55, coins:rpc_clients:1864] INFO Electrum client connected to zeta-seed-c.zetacoin.tech:50012
07 09:06:55, coins:rpc_clients:1726] ERROR expected value at line 1 column 1
07 09:06:55, coins:rpc_clients:1726] ERROR expected value at line 1 column 1
07 09:06:55, coins:rpc_clients:1726] ERROR expected value at line 1 column 1
07 09:06:55, coins:rpc_clients:1726] ERROR expected value at line 1 column 1
07 09:06:55, coins:rpc_clients:1726] ERROR expected value at line 1 column 1
07 09:06:55, coins:rpc_clients:1726] ERROR expected value at line 1 column 1
07 09:06:55, coins:rpc_clients:1726] ERROR EOF while parsing a value at line 1 column 1
07 09:06:55, coins:rpc_clients:1726] ERROR expected value at line 1 column 1
07 09:06:55, coins:rpc_clients:1888] INFO EOF from zeta-seed-c.zetacoin.tech:50012
07 09:06:55, coins:rpc_clients:1930] INFO zeta-seed-c.zetacoin.tech:50012 connection dropped

this happens without pause several times in a second
to fix, coin needs to be disabled, bad electrum server removed and re enabled

question is: can mm2 make a pause of at least 1s before retrying in such cases? :-)

[artemii235]

@cipig Thanks for opening the issue! I plan to work on Electrum client improvements this week. I will check this report too.

[cipig]

It turned out i was told the wrong port... port 50012 was the WSS port of this electrum, so i connected with SSL to the WSS port, which led to the above error... but maybe still worth adding some additional check in mm2, to prevent it from dying when you accidentally connect to wrong port or person running the electrum server accidentally changes something... wouldn't be good if i can kill all mm2's by pointing SSL port to WSS port :-)

[artemii235]

Fixed in the linked PR. Thanks for the report!