I'm looking for some software to monitor packet loss or packet retries.  Preferably something that continuously monitors vs. a testing approach  and preferably free.   My server's OS is debian. I'm not sure if wireshark can do this since I don't have access to a graphical interface on my server, only text/SSH.  Any suggestion please ?
122660
How can I passively monitor the packet loss on TCP connections to/from my machine?  Basically, I'd like a tool that sits in the background and watches TCP ack/nak/re-transmits to generate a report on which peer IP addresses "seem" to be experiencing heavy loss.  Most questions like this that I find of SF suggest using tools like iperf.  But, I need to monitor connections to/from a real application on my machine.  Is this data just sitting there in the Linux TCP stack?
67191
I am looking for system monitoring tools which are GUI and CLI or web-based which include basic functions such as:   CPU Usage Ram Usage Swap Usage Disk Usage ( Space / I/O ) Heat Monitoring   I know there are many tools I can use, but I am looking for a single tool that has these basic functions.
87569
When using Google chrome there is a handy network monitor tool. However the chrome network tool only keeps track of the current open webpage.    There are a lot of complicated network monitor tools available and I only need the features of the chrome network monitor tool.   To keep track of all the browsers (Chrome, Firefox, IE etc.) activity I am searching for a tool that has the same idea and interface as the chrome network tool.  Someone knows a tool like that?    Some screenshots with the wished features:  A overview of all the files downloaded   when selecting a file you can nicely see the headers   And with the tab response the content of the body is visible
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I have an old PC lying around which I've installed Debian 6.0 on.  Last night I was trying to SSH in and it wouldn't respond so I pressed the reset button.  How can I find out what happened to it?  It seems fine now.
35897
What's the best approach towards determining if I have a rogue DHCP server inside my network?  I'm wondering how most admins approach these kinds of problems.  I found  through searching, and thought about trying it out.  Has anyone had experience with it? (I would like to know before taking the time to compile it and install).  Do you know any useful tools or best-practices towards finding rogue DHCP servers?
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I use an SSH tunnel from work to go around various idotic firewalls (it's ok with my boss :)). The problem is, after a while the ssh connection usually hangs, and the tunnel is broken.  If I could at least monitor the tunnel automatically, I could restart the tunnel when it hangs, but I haven't even figured a way of doing that.  Bonus points for the one who can tell me how to prevent my ssh connection from hanging, of course!
97032
I want to make a log to detect the nature of intrusions into my Unix/Linux based server.   For that I want to learn some tools like Open Source Tripwire and OSSEC. Please suggest to me similar tools.   What kind of info can I get about the intruder from the tools of this kind? Can I automate the process of keeping track of the alerts generated by these tools in a file?
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Is there a command line based way to send pings to each computer in a subnet? Like  for(int i = 1; i &lt; 254; i++)     ping(192.168.1.i);   to enforce arp resolution?
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Running, either in promiscuous mode or not :   tcpdump -i "$INTERFACE" -vvv -n -XX -S -s0 -e   I got a bunch of lines and this conclusion when I stopped it :  601 packets captured 938 packets received by filter 230 packets dropped by kernel   Why the difference ? Where are the 107 packets missing ? And is it possible at all to get/capture 100% of the packets on the local network - it's just me behind a router ?
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I'm reverse-engineering a serial protocol and getting frustrated by bad tools.  Does anyone know of a good, free tool for logging data to/from serial ports on Windows?  Requirements:   Must be free Must not take control of the port (i.e. must hook the file APIs or the kernel rather than trying to open the device) Must have some sort of filtering features Writes either human-readable or binary logs, preferably in an easy to parse format   Any ideas?  Portmon works, but its logs are difficult to work with and its filters are effectively useless; I've also tried a few commercial tools and nothing seems to fit the bill.
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Is there a good  (free telnet / ssh client) equivalent for OS X?  I know that I can just use terminal and an ssh command, but I want some sort of application that will store connection info, passwords, logs, etc for me, much like PuTTY.  Does this exist?
42789
I'd like to do some general disk io monitoring on a debian linux server. What are the tools I should know about that monitor disk io so I can see if a disk's performance is maxed out or spikes at certain time throughout the day?
18960
I have a home server which needs a mail server for error messages, mostly.  I used postfix but I find the features/complexity compromises not optimal for my home server: there are tens of lines to check/configure, stunnel to install for TLS, ...  What simpler mail server with TLS support can I use, that is also packaged by Canonical? I'm going to only use an external relay server provided by my provider.
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Ok, I realize this situation is somewhat unusual, but I need to establish a TCP connection (the 3-way handshake) using only raw sockets (in C, in linux) -- i.e. I need to construct the IP headers and TCP headers myself.  I'm writing a server (so I have to first respond to the incoming SYN packet), and for whatever reason I can't seem to get it right.  Yes, I realize that a SOCK_STREAM will handle this for me, but for reasons I don't want to go into that isn't an option.  The tutorials I've found online on using raw sockets all describe how to build a SYN flooder, but this is somewhat easier than actually establishing a TCP connection, since you don't have to construct a response based on the original packet.  I've gotten the SYN flooder examples working, and I can read the incoming SYN packet just fine from the raw socket, but I'm still having trouble creating a valid SYN/ACK response to an incoming SYN from the client.  So, does anyone know a good tutorial on using raw sockets that goes beyond creating a SYN flooder, or does anyone have some code that could do this (using SOCK_RAW, and not SOCK_STREAM)?  I would be very grateful.    MarkR is absolutely right -- the problem is that the kernel is sending reset packets in response to the initial packet because it thinks the port is closed.  The kernel is beating me to the response and the connection dies.  I was using tcpdump to monitor the connection already -- I should have been more observant and noticed that there were TWO replies one of which was a reset that was screwing things up, as well as the response my program created. D'OH!  The solution that seems to work best is to use an iptables rule, as suggested by MarkR, to block the outbound packets.  However, there's an easier way to do it than using the mark option, as suggested.  I just match whether the reset TCP flag is set.  During the course of a normal connection this is unlikely to be needed, and it doesn't really matter to my application if I block all outbound reset packets from the port being used.  This effectively blocks the kernel's unwanted response, but not my own packets.  If the port my program is listening on is 9999 then the iptables rule looks like this:  iptables -t filter -I OUTPUT -p tcp --sport 9999 --tcp-flags RST RST -j DROP
26701
I use Hotspot Shield (Free VPN) on the Windows. Do anyone know of a similar tool or service for Ubuntu?  that:   Would not require me to have any server. would hide my IP. Would effectively tunnel all my connections in Ubuntu. have free plans   please explain pros and cons of your suggestions.
9867
I am running Wireshark on my linux machine and i have simple python web server running on localhost:8080  I am capturing only local port 8080. When i open browser on localhost:8080 wireshark captures huge amount of tcp communication (as page loads with all resources) but there`s no HTTP only TCP...   Why i cannot capture HTTP on custom port ?
65139
Is there a way to benchmark how fast my router is connected to my PC, independent of the internet?  I've had slower-than-usual internet-based benchmarks, and I'm having a hard time figuring out if it's because of a bad router-to-PC connection (interference, bad signal, etc.) or if it's indeed because my internet is actually slower.