Tagged Questions
1
vote
2answers
46 views
Checking if I can reach some ports from my computer
Is there a terminal command or something on OSX that I can use to test if I can reach some ports on a remote server?
I know these ports are reachable on that server, because I can access them from ...
0
votes
0answers
42 views
What could be the possible reasons for bad performance of TCP over Wireless or Sate-lite networks ?
I am running a wireless network having Linux(fedora 17) at sender end.We decided TCP_veno is most useful for my network,so we are using it as default congestion control algorithm.Still, We are not ...
0
votes
1answer
29 views
What are the other congestion control algorithms specially designed for lossy Wireless Networks like LTE and WiMax?
I am trying different congestion control algorithms for getting maximum throughput and minimum delay across my setup for TCP flow.Please suggest other available algorithms apart from
Veno, ...
21
votes
1answer
437 views
Why does it take up to several minutes to clean a listening TCP port after a program dies?
If I kill a program that is listening on a TCP port, it takes up to several minutes until the port is reclaimed by the system and usable again. I've seen several Q/A mentioning this phenomenon, but ...
1
vote
2answers
237 views
Why TCP TIME-WAIT State is present at both ends after a connection termination?
I am reading how the TCP states work and especially the connection termination part.
All of the books or online material I read, shows that for the termination procedure these states are followed ...
3
votes
2answers
280 views
Getting current TCP connection count on a system
Instead of doing wc -l /proc/net/tcp, is there a faster way of doing it?
I just need a total count of tcp connections.
0
votes
0answers
38 views
How to tune Unix (Ubuntu) for web crawling?
What are some ways to tune some Unix settings in the kernel(or elsewhere) for web crawling purposes? I am using multi-curl, and am using a multi-threading approach. I've set a higher limit for maximum ...
1
vote
1answer
127 views
Default value for SO_RCVTIMEO option on Solaris
Is there any way to find out what is the default value set for option SO_RCVTIMEO on Solaris 10?
If there is a way to find out how would one go about changing it?
P.S. I am aware of ability of ...
2
votes
1answer
166 views
Running a local port scan and found open ports but, don't know what they're used for?
I wrote a very basic python script to port scan my system. I'm running linux-mint lisa:
open_ports = []
for port in xrange(65536):
conn = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
...
1
vote
1answer
333 views
Is there a faster interface for info from /proc/net/tcp?
Given a linux TCP socket's inode (obtained via /proc/<pid>/fd), is there a faster way to look up the information that I can get from /proc/net/tcp about this socket?
I have written a ...
3
votes
2answers
233 views
Meaning of log entries from an iptables configuration
My router has Linux as its OS. The system log has a lot of rows about iptable and klogd that I don't understand, could someone explain them to me?
The iptables setup:
iptables -t nat -A PREROUTING ...
12
votes
4answers
564 views
TCP dies on a Linux laptop
Once in several days I have the following problem. My laptop (Debian testing)
suddenly becomes unable to work with TCP connections to the internet.
The following things continue working fine:
UDP ...
2
votes
2answers
2k views
Fast way to copy a large file on a LAN
I am having some trouble with NFS, and I'd like to try using just plain old TCP.
I have no idea where to begin, though.
Hardware-wise, I am using an ethernet crossover cable to network two netbooks.
...
4
votes
3answers
287 views
How can I know the process name which is opening a tcp port?
I have two linux servers. Let's say they are C and S.
C is client of S
On my S machine, I type.
$ netstat -an | grep ESTABLISHED
tcp 0 0 192.168.1.220:3306 C:57010 ...
3
votes
1answer
223 views
Route incoming network requests for a given port to different applications
I have an application that listens for connections on a port, but I occasionally take it down for updates and the like. I'd like a way to configure the system such that if that program is running, ...
3
votes
1answer
271 views
User associated with a socket
I use ss -p to see TCP sockets information. But process info are not printed for some sockets. Below:
$ ss -p4
State Recv-Q Send-Q Local Address:Port Peer Address:Port
ESTAB 0 0 ...
1
vote
1answer
281 views
How to limit all tcp traffic to the network interface the session was initiated on?
I have an embedded linux system with two network interfaces (lan0, wlan0) that are configured to the same subnet. A server on this system accepts tcp connections on both interfaces.
How I can assure ...
2
votes
3answers
1k views
Trying to Open a Port using CentOS
(I'm new to this!)
I'm running a virtual server running CentOS. I'm trying to run a server that listens on port 37760. The code I'm running executes successfully, so I run
netstat -lptu
To show a ...
1
vote
1answer
434 views
Port Mirroring in Fedora?
I have set up an application that listens constantly to a port for network packets, and I would like to create another one that receives the same network packets ( for use as a test bed). Getting the ...
0
votes
1answer
2k views
How to run tcptraceroute utility on UNIX machine?
How can I run the tcptraceroute utility on a UNIX machine?
I want to run a TCP traceroute for port 80.
8
votes
1answer
498 views
what level of the network stack does tcpdump get its info from?
As I was trying in vain to fix a faulty ethernet controller here, one thing I tried was running tcpdump on the machine.
I found it interesting that tcpdump was able to detect that some of the ICMP ...
8
votes
2answers
1k views
minimal TCP MSS in Linux
The TCP MSS in Linux must be at least 88 (include/net/tcp.h):
/* Minimal accepted MSS. It is (60+60+8) - (20+20). */
#define TCP_MIN_MSS 88U
My question is: where did they come up with ...
0
votes
1answer
756 views
How to do “netcat” relays properly so that I have more control?
How to use the netcat to have relays? Like following I tried but not working:
cd /tmp
mknod backpipe p
nc -l -p 7007 0<backpipe | nc 192.168.1.101 9001 | tee backpipe
I want to receive data on ...
4
votes
3answers
1k views
IPTables and transparent proxies
I have set up a local, transparent TCP proxy on localhost. I want to redirect ALL TCP traffic to this proxy, so it can handle it and nothing "leaks out," circumventing the proxy. I need to use ...
12
votes
1answer
3k views
Why are the first 1024 ports restricted to the root user only?
This is more idle curiosity than anything else. A friend of mine asked me 'which port range is it that only root can use under Linux?' I told him 0-1024 were restricted. Then he asked my why it was so ...
14
votes
2answers
5k views
how to check rx ring, max_backlog, and max_syn_backlog size
Quite often in the course of troubleshooting and tuning things I find myself thinking about the following Linux kernel settings:
net.core.netdev_max_backlog
net.ipv4.tcp_max_syn_backlog
...
13
votes
5answers
8k views
Linux: allowing an user to listen to a port below 1024
I need to allow an user (different from root) to run a server listening on port 80.
Is there any way to do this?
3
votes
1answer
687 views
Simple way to create a tunnel from one local port to another?
I have a development server, which is only accessible from 127.0.0.1:8000, not 192.168.1.x:8000. As a quick hack, is there a way to set up something to listen on another port (say, 8001) so that from ...
8
votes
2answers
21k views
Orphaned connections in CLOSE_WAIT state
I've got a SLES machine that accumulates TCP connections in a CLOSE_WAIT state for what appears to be forever. These descriptors eventually suck up all available memory. At the moment, I've got 3037 ...
8
votes
5answers
8k views
Determining what process is bound to a port
I know that using the command:
lsof -i TCP
(or some variant of parameters with lsof) I can determine which process is bound to a particular port. This is useful say if I'm trying to start ...
