TCP stands for Transmission Control Protocol and is one of the core protocols of the Internet Protocol Suite. TCP complements the Internet Protocol (IP), and therefore the entire suite is commonly referred to as TCP/IP.

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313 views

Unix socket connection limit

This may appear like an already discussed/answered question. But I am specifically looking for info which I couldn't find anywhere answered clearly. I have an Nginx + php-fpm setup which uses unix ...
1
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1answer
323 views

trace ftp file data in wireshark

I am trying to analyze ftp traffic in Wireshark. I can see commands like Request: List, PORT. But after FTP Response 150: Opening data channel for directory list. what I see immediately is ...
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1answer
717 views

Why do some connections time out and others get refused?

I have noticed that sometimes while trying to telnet in some random port, I have observed two kind of scenarios: $ telnet example.com 3432 Trying 173.252.110.27... $ telnet example.com 3432 ...
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1answer
176 views

iptables NAT Forward 443 Port DNAT,SNAT failing

I'm trying to setup a proxy server that handles http and forwards https to the webserver. Client > Proxy > httpd I added the rules: iptables -t nat -I PREROUTING -i eth1 -p tcp -m tcp --dport ...
0
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1answer
126 views

syslog-ng 2.0.9 closing tcp connections from some clients instantly..?

I've a syslog-ng instance on 2.0.9, which is old, but... this is enterprise IT and upgrading the versions is... fun... running on Solaris 10. I have this strange problem where some clients stop being ...
2
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1answer
401 views

How to tune Windows 2008r2 and IIS to maximize single file download speeds?

We recently put up an IIS site (on WinSvr 2008r2 running as a Hyper-V guest) that is used almost exclusively for downloading files over the internet. The data exists as a large collection of .zip ...
2
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1answer
2k views

Netstat -s showing (and growing) “packets pruned from receive queue” and “packets collapsed in receive queue”

we are seeing the following: [root@primary data]# netstat -s | grep buffer ; sleep 10 ; netstat -s | grep buffer 20560 packets pruned from receive queue because of socket buffer overrun ...
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2answers
161 views

How can I release a port that is still in use but not bound to a process?

I'm running a Python application that spawns multiple processes. It uses port 56008 to listen for client requests. Sometimes after closing it the port it used is still "in use". There are still some ...
5
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1answer
738 views

How to expose a UNIX domain socket directly over TCP

I'd like to have a UNIX domain socket, say /var/program/program.cmd for example, exposed via TCP, lets say on port 12345. I'd also like this to be running full time in the background. What's the best ...
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0answers
51 views

IIS6 poor throughput from higher latency

I've been having a crazy issue with Windows 2003 + II6 where the throughput goes down as the latency goes up. This is exactly the type of thing that TCP Window scaling is supposed to solve so I ...
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2answers
208 views

Can a duplicate computer name be known before attempting to join the domain?

Techs in the field are deploying windows 7 pcs onto a domain. They complete one entry screen, which should give them a unique computer name. However, they are human and end up giving the pcs the ...
3
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1answer
330 views

problems simulating TCP SYN flood

I'm trying to simulate a TCP SYN flood to tune a web server (planning to deploy on AWS). I setup a 'target' VM, disabled iptables and running hping (hping -p 80 -i u1000 -c 1000 -S destaddr) from ...
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1answer
2k views

tcpdump capturing tcp resets by host

I am trying to figure out where my tcp resets on my webserver happen. I have the following capture: tcpdump -fnni bond0:-nnvvS -w dump.pcap 'tcp[tcpflags] & (tcp-rst) !=0' When I look at the ...
4
votes
1answer
7k views

Why does WireShark think this frame is a TCP segment of a reassembled PDU

Please find a small pcap file here illustrating my problem. I have a three-way TCP handshake, followed by two FIX logons. (FIX is a protocol used in trading.) The first FIX logon (frame 4) is ...
4
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1answer
156 views

HaProxy for game servers, what's wrong with my configuration?

I host a website with a game client that uses TCP for connections. I am currently looking for a way to proxy my connections from one server to my origin server. I have tested Iptables forwarding and I ...
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1answer
64 views

TCP Implementation in Micrsoft Windows XP + 7 [closed]

I'm looking for the TCP implementation in MS Windows, especially for Windows XP and 7 in case they are different. To be more specific, I'm interested in the following parts of the TCP implementation: ...
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2answers
276 views

Linux : Send a tcp message to a url/endpoint [closed]

I want to send a xml message to a URL like tcp://localhost:6060/services/test What are the available tools for this?
3
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1answer
347 views

Enabling TCP md5 signature option in centOS?

I'm trying to enable md5 checksum/signature for tcp packets in centOS (the main use case to stop tcp RST attacks, etc). It seems like I may be able to do this for individual ports using netcat or via ...
1
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1answer
98 views

can I filter TCP SYN packets with seq=0

My servers appear to be targeted by a SYN-flood attack. Between 50-600MBit/s, spoofed IPs. Packets look like this: IP p.q.r.s.1234 > my.ser.vers.ip.80: Flags [S], seq 0, win 5840, length 0 with ...
0
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1answer
1k views

Newbie, need help deciphering firewall log files (Cisco ASA 5520)

I'm not very familiar with firewall log files, or many of the terms involved in server connections. The lines in question involve a foreign, unauthorized IP interacting with a firewall (Cisco ASA ...
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0answers
122 views

Only ICMP traffic allowed inbound on ISA Server 2006

I have recently set up a connection to a remote site. The connection between the sites is done at the ISP level (ie, this is not a B2B tunnel on ISA). I'm fairly lightweight in the networking realm, ...
2
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2answers
98 views

Minimal size of TCP communication

I am sending small amounts of data (up to 100 bytes) every 10 minutes from devices to TCP server. In my case overhead seems to be huge (we pay for each byte). I found that I have at least 7-10 packets ...
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3answers
113 views

TCP application accessible remotely but not locally

I am trying to help a friend figure this out, so I don't know all the details, but I figured I would post on here to see any possibilities. We have a custom application that communicates using a ...
0
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1answer
224 views

How do I change the source address of a tcp packet?

Is it possible to change the source address of any TCP packet ? I am aware of the fact that I will not receive those packets if I change the address, I only need to place a request on the server. How ...
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1answer
207 views

Can't connect to my own machine through public IP

I couldn't figure out why I can't make a connection through my public IP. When using a local IP it works. I have the proper firewall port exceptions, and my router NAT has the configurations for port ...
3
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1answer
463 views

How to debug why WAN TCP/IP throughput is lower than expected?

I'm trying to figure out why tcp/ip throughput between two hosts I control is much lower than expected. Host A: internet connectivity provided by Comcast (Residential) in Boston Metro -- can ...
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1answer
50 views

How to host a TCP / UDP service on the Internet which is currently running on my local machine? [closed]

I have created a TCP server and it's currently hosted on my local machine, but I want to host it on Internet like we host websites. Is there any company which provides this service? And what's the ...
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1answer
111 views

Will traffic control software cause tcp packets to be dropped

I am testing our client-server applications using NetLimiter which is a traffic control software. I found that, when client is receiving files from server and I use NetLimiter to set the download rate ...
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3answers
273 views

Max client TCP connections through a router

I've just been thinking about what the maximum number of client connections would be out of my home LAN to a single server on the internet. My home router is also NAT'ing the connections to convert ...
0
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1answer
173 views

Socket based byte counts

I see a lot of tools to get the RX and TX byte counts for transmission on interfaces, is there any tool/program that I can use to get a total transmitted byte count for a single specified socket? I'm ...
2
votes
2answers
2k views

Reduce firewall rules by half - one iptables rule for tcp and udp

I have a number of iptables rules on my firewall that look like this: iptables -A zone_lan_forward -p tcp -d 1.2.3.0/24 -j ACCEPT iptables -A zone_lan_forward -p udp -d 1.2.3.0/24 -j ACCEPT Is ...
9
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3answers
1k views

Lower TCP throughput from 1Gbps server than 100Mbps server over large RTT

We've got infrastructure distributed in a few major locations around the world - Singapore, London and Los Angeles. The RTT between any two locations is over >150ms. We've recently upgraded all of ...
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4answers
615 views

Can I find out what certificate revocation server an application is contacting?

I'm trying to install an application on a machine running Windows XP Pro. There are two different servers being contacted, both using the same wildcard certificate (GoDaddy). One via https, one ...
0
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1answer
110 views

Minimal handshaking necessary before establishing TCP connection

I have a Windows PC that is running a TCP server on port 9000. I also have an FPGA which is directly connected to the PC via a 10G port. The FPGA can send ethernet frames to establish and maintain a ...
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4answers
850 views

Rsyslog not logging from remote server

I am trying to set up a centralized log server. I have central server (A) receiving logs via a remote server (B) on port 514. I know it is receiving these. Here are a few entries from a tcpdump on ...
2
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1answer
408 views

How to force use of tcp instead of udp for rpcbind?

I'm trying to use tcp/111 for rpcbind under Debian Wheezy instead of udp/111. The portmap in Squeeze uses tcp/111 without any special configuration, but Wheezy fails. Even numerous sites (as well as ...
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4answers
263 views

Why is the TCP checksum inverted?

From the Wikipedia page: The checksum field is the 16 bit one's complement of the one's complement sum of all 16-bit words in the header and text. Why, after summing the 16-bits in the header ...
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2answers
287 views

TCP vs UDP Error-Checking

I've bounced upon two articles that describe in-depth on how TCP and UDP connections work. However there is some kind of inconsistency. Where one article tells me that UDP does no Error-Checking at ...
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100 views

tcp recycle and retransmission

TCP recycle reduces TIME WAIT by reusing sockets. It avoids collision with older packets by storing timestamp and receives packets with greater TCP timestamp. What happens when the client retransmits ...
0
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1answer
95 views

What process does 'own' socket in 'Time Wait' state?

Main question I see following line in netstat. Does it means this socket doesn't belong to any process? #>netstat -tpn|grep TIME_WAIT| head -1 tcp 0 0 ::ffff:127.0.0.1:5555 ...
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1answer
194 views

TCP RWIN, MSS and MTU [closed]

I have been doing some reading into TCP Receive Window (RWIN), Maximum Segment Size (MSS) and Maximum Transmission Unit (MTU). Right off the bat I have some questions and I need a power user's help! ...
3
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1answer
207 views

How to disable Xvfb using TCP ports when using pyvirtualdisplay (Python)?

Trying to use pyvirtualdisplay for Python to start some applications with a virtual Xvfb X terminal. However, we've seen port clashes and would like to disable Xvfb from using TCP ports. I have ...
2
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1answer
27 views

TCP Reno Window Size drops to 0

I'm working on a task on comparing TCP Tahoe and Reno. Tahoe drops the window size to 0 every time it detects packet loss, that is clear. However, when I plot my window size for Reno, it does fast ...
1
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1answer
282 views

TCP/IP routing: accessing a LAN device with wrong static IP configuration

I forgot to change the static IP of a network device before moving it from my datacenter network to my home LAN. Since it isn't configured properly for my LAN network, I'm not sure how to access it. ...
0
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0answers
73 views

Cant connect to mysql server

I'm trying to configure a freshly installed mysql server to listen on port 3306. I've removed skip_networking, I have changed bind-address=172.20.33.1 (which is my server ip) and it completely ...
0
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2answers
929 views

How do I get my ubuntu server to listen for database connections?

I am having a problems connecting to my database outside of phpmyadmin. Im pretty sure this is because my server isn't listening on port 3306. When I type: sudo netstat -ntlp on my OTHER working ...
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2answers
44 views

Three Duplicate acknowledgements

I understand the process of congestion avoidance where you trying to control the level of congestion in a network, and avoid loss of packets. But how can there be three acknowledgements, even if one ...
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1answer
118 views

svnserve -d child process spawning and svn connections under netstat

I see many svnserve -d processes running on my CentOS 6 box, one with the PID 400 and PPID 1 and the rest with PPID 400. I take this to mean the first one is started by init scripts (i know it is) ...
2
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2answers
2k views

Traceroute, ICMP, UDP and TCP

When does traceroute use TCP? Or does it just use UDP, also why does Traceroute use UDP on MacX and ICMP on windows? I thought ICMP just contains a message saying what caused the error of a packet and ...
0
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0answers
365 views

How to interpret findings on TCP Send/Recv Buffers

I have an application running on a CentOS machine that connects to a remote DB server on another CentOS machine. Every once in a while, without any discernable warning signs, the application seems to ...