Threads_connected too high, closing slowly and db slow

[F G]

Hello,

i have a large (about 70Gb) mysql database with mainly innodb tables. i use the option INNODB_FILE_PER_TABLE and recently moved the database to a new server. the new server is about 4 times as powerful (cpu and ram) as the old one.

since i use the new server some weird behaviour has shown up. i am running tools (.net) accessing the database. these tools open and close connections permanently, but there should never be more than 50 concurrent connections open. after a few minutes the tools start to be very slow or fail and new connections to the database fail with a timeout or with a message like 'too many connections'. THREADS_CONNECTED is always the number of the max connections allowed. when stopping all tools the connections don't get closed immediately but takes about 20 to 30 minutes (with only 256 connections) to reach the minimun connections. this never happened on the old server, thus shouldn't be a problem of the tools or too little computing power of the server.

did i do something wrong with the configuration or could it be the server change? i guess i should provide some more info about my configuration but i don't know which ones are helpful.