Not sure what that means. Networks are serial of course. They handle multiple requests, but serially. Presumably "concurrent connections" means open sockets - perhaps because you are not sure that the server is keeping them open? Or perhaps because firewall(s) might be dropping requests if limits are exceeded? If you are not sure which, then if it was me, I would want to check with the actual server rather than a general tool. Since the server application itself could be the problem rather than the network and/or firewalls. Rather simple to write code to do database (relational) connection testing. Just open connection and do simple do nothing query in a loop. Then wrap that in a loop for multiple connections. More difficult for modern usage besides database since it is usually ReST (http) because the connection closes after the request. Thus what you really need to do is identify a rest call that takes a while. And really if you cannot do that they you need to put a Rest call in place that does take a while. Perhaps having it do nothing but return ok and have a sleep for 5 seconds or so before it returns to the ok. I will note that you could write http code that would keep the connection open but that is not normal and as such seems suspect to test in the first place. If you can't control the server then you are going to need to bombard it with requests and that could incorrectly report results for normal firewall rules put into place to prevent DNS attacks. Any tool of any sort requires understanding, configuration and even some messing about to get it up and running correctly. Also why a "range of ports". Servers do not typically support more than several ports and functionality and even rules are different. Certainly shouldn't be doing performance testing on an app unless you know what that app does. Just a warning, 'port scanning' is something that network infrastructures will flag and anomalous behavior and if it was me I would not do that unless I had it in writing (actual paper) from a superior that that is what they wanted done. That can lead to civil and criminal penalties and you want to be protected.
