We're attempting to track down an issue a client is having with injecting large quantities of mail to our gateway, and somewhere along the line, his connections are being rejected. Unfortunately, beyond that, the client has not provided much useful data other than that he doesn't seem to be getting SYN ACK messages back.
We're looking to do some testing of our service and establish just how many TCP connections it can establish (and later, messages we can inject) before it chokes. Are there any utilities which I could use to establish thousands of simultaneous TCP connections to a target? No payload is necessary.
Ideally, this tool would give us a rundown of how many connections it was able to establish, or how rapidly, etc.
Any thoughts are highly appreciated!