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Questions tagged [tcp]

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.

TCP is just one communications protocol on the web. Others include:

  • User Datagram Protocol (UDP)
  • Internet Control Message Protocol (ICMP)
  • Hypertext Transfer Protocol (HTTP)
  • Post Office Protocol (POP3)
  • File Transfer Protocol (FTP)
  • Internet Message Access Protocol (IMAP)

TCP on Wikipedia

1636 questions
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ssh tunneling lmgrd port what I've missed?

I've got 2 machines: one local , one flexserver I'd like to do a ssh connection for forwarding the TCP port of the flexserver. On the flexserver, lmutil lmstat -c 5280@localhost is working fine So I launched the ssh tunneling connection: ssh -N -L…
dubis
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How to ping a host with different MTU size to simulate icmpv6 packet too big scenario?

As the Title states,I want to check whether my host will actually send a ICMPv6 packet too big if i send a packet with beyond the defined MTU size.I don't have a cisco router(extended ping) to try out the scenario,Hence i would like to inject the…
Renold
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Forwarding ports and traffic to VPN tunnel

I've installed OpenVPN on my VPS. I have one question: how to forward traffic going to that VPS to go to VPN tunnel created with my local PC. I will use TCP connection. The whole traffic will be like Internet -> VPS -> VPN tunnel -> my PC. I think…
Matúš König
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TCP ACK Window shrinking

(Note: I am not a networking engineer) We are sending files to an outside vendor and getting random timeouts on different services. It seems that we are getting timeouts most often on larger files. We did a packet capture that shows our window…
Buzkie
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what could cause a not so busy redis server to close connection?

We have 17k tcp connection in CLOSING state on redis server. My understanding is that only client would initiate closing a connection, not from a redis server. So I should see 0 connection in CLOSING state on redis server. Does anyone have some…
Chuan Ma
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TCP connections drop off after initial build up

A bizarre problem on a production setup. Scenario 1) A server listens on a particular port. 2) There are potentially thousands of TCP connection requests. 3) About 200-300 TCP connections reach ESTABLISHED state (netstat output). 4) After this, the…
TheMonkWhoSoldHisCode
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Forwarding HTTP requests from old server to new server

I am moving many sites from an old web server to a new one. It needs to be done as transparently as possible. The sites are backed by a WCMS, so there is a possibility that clients can make changes to what is actually their old site. To avoid this,…
Zimmy-DUB-Zongy-Zong-DUBBY
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A LOT of connections from my external IP address to my web server

I installed Nagios recently on a Debian machine running an Apache web server among other things. The thing is that lately, Nagios tells me that the HTTP service is failing intermittently and it seems that, at random moments, the server gets A TON of…
Imanol Barba Sabariego
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How do I open specific ports on Linux (an AWS instance of RHEL v. 7)?

I'm using RedHat version 7. My AWS instances are in a security group with ample permissions for inbound connectivity. I can do Yum updates. The servers can ping each other. I can transfer files from my workstation to the servers. I even…
Propulsion
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SNORT only alerting on inbound traffic

I am trying to raise an alert when someone is setting up a connection to PORT 25 (tcp), whatever source or destination. For this i came up with this simple rule: alert tcp any any -> any 25 (msg:"Email sent"; sid:10001337007;) From a Windows client…
Tommy
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Windows Server 2008 sending regular TCP DNS requests to Forwarders

Our organization's primary DNS server is a Windows Server 2008 which two Forwarders set. I happened to notice on our firewall that this server is sending out regular TCP requests to the Forwarders in addition to the standard UDP queries. I ran…
Andrew S
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length of Tcp segment exceed MSS

I find a weird behavior in my Linux system, when I curling a web page, the received TCP segments are significant larger THAN the MSS. here is the output of tcpdump: 00:00:00.000000 IP 10.15.71.190.44503 > 115.239.210.27.80: Flags [S], seq…
Sgra Ekim
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Cisco ASA firewall blocking requests to internally hosted DNS server

I have a DNS server behind a Cisco ASA firewall. The Cisco firewall is performing NAT. When inside the network, I can NSLOOKUP directly to the server. When the client is external, requests time out. Assuming the internal IP Address of the DNS…
user1955162
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how to determine client side or server side retransmission from a pcap

I am trying to get some clarification on something I read here: how to calculate packet loss from a binary TCPDUMP file The first answer says that the sequence number will be the same from client to server and from server to client the ack would be…
user53029
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How to use tcpdump to log only certain data in real time

I'd like to monitor network interfaces, but only log things likes errors, collisions and dropped packets and send that to stdout. Can tcpdump be configured to do this?
user53029
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