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4

if you want to ssh your instance without NAT, it has to be reachable from your network (where your laptop is). thus I see two solutions: set an elastic IP to your instance + internet gateway/route to your subnet. An elastic IP without internet gateway is not enough, as traffic will not be routed properly. However, if you set up an Internet gateway, the NAT ...


2

If it's available or can be installed, take a look at netcat. You could do something like this. On the server run: nc -l 31415 On the client run: nc -w 5400 <server> 31415 You can change the port number to anything you like, just make sure you can reach it from where you are testing. A timeout of 90 minutes (-w 5400) is set in the example ...


0

My standard guidance here is if you want this level of isolation, just use two JVMs. It's unclear if you care about TCP connections or concurrent requests. The only way to limit either of these is to create a new TCP endpoint and assign it to a new, non-default threadpool. You would then map the special app to a new virtual host that only has a host ...


2

If you are debugging connectivity(Layer 3) you need ping and traceroute. If you want to check open ports you need tcptraceroute(Layer 4 TCP) or nmap (Layer 4 TCP/UDP), but it's pretty hard to debug UDP. openssl s_client -connect will help you to debug SSL(Layer 5). For everything else use tcpdump/tshark.


3

Layer 2 requires layer 1 and layer 3 requires layer 2. Everything above that requires a functioning transport layer (3) and therefore tests above that are application specific and will vary between what type of service you are running. Like you have already said, telnet which is an application so layer 7 is a handy way of testing socket connectivity between ...


0

You need to create a new instance to fix the iptables. Follow the guide here(scroll down a bit): https://aws.amazon.com/articles/5213606968661598 Then add a script updating the iptables into the rc.d folder so it runs at launch Sync & Detach the volume. Reattach to the old instance. Start and hopefully it has worked. Done. Little note: There is ...


0

If it wasn't on AWS, you'd just need to log in on the console of the Linux server and add back the missing rule from there. Regrettably, AWS doesn't provide console login access to instances, so you'll have to follow the steps described in the AWS tutorial How to Recover an Unreachable Linux Instance to regain access.


1

Actually, you are asking how to protect from DDOS attack. It's really depends on amount of traffic/packets to your system. I believe it's TCP syn flood in your case. You need to check amount of pps and traffic with iptraf(iptraf -d eth0 for example). Also you should look at sysctl: net.ipv4.tcp_syncookies net.ipv4.tcp_synack_retries And enable ...


2

As for my understanding of TCP, asserting "Keeping TCP connections alive" is misleading, as there is no TCP-protocol-specific mechanism dealing with timeout, when referred to ESTABLISHED connections. I mean: once established, they can last forever, until a RESET, a FIN or a timeout in receiving an ACK (...following some transmission to be ACKnowledged, in ...


1

Your idea is fine; in fact, modern mobile devices use the exact same approach for their notifications, they maintain a permanent connection to the OS developer's server and that server pushes notifications down that connection (third-party app developers send notifications to the OS's developer which in turn relays them to the appropriate mobile device). An ...


0

Nope. The kernel doesn't store that kind of info.



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