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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8
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5answers
625 views

dump tcp connections without tcpdump

On a centos box, I like to dump tcp connections - I would like to see if a server tries to send requests to a certain IP. Usually tcpdump would do the trick - but tcpdump is not installed, and ...
0
votes
1answer
57 views

TCP RST from telnet/ssh daemons when connecting from openvpn

I have LAN_1 and LAN_2 interconnected with an openvpn tunnel terminated ona pair of SOHO routers running busybox. One of the vpn purpose is to allow clients on both LAN_1 and LAN_2, to administer the ...
6
votes
1answer
123 views

How does Intel AMT (Active Management Technology) not interfere with the TCP/IP host stack?

The Intel dev kit I've been using includes a remote management feature (also see the Ubuntu man page here) which allows remote reboots in case the operating system hangs. It has the capability of ...
2
votes
1answer
188 views

Cisco ASA 5510 Out-of-Order Packets to Google

We're seeing a large number of packets being dropped due to being Out-of-Order. The numbers are large enough that it may be having an impact on network performance. We've isolated it down to a few ...
1
vote
1answer
167 views

How to configure SSH client timeout after network failure?

Let's say I connect from a client to a server via SSH, and in the middle of the session I pull the server's network cable. On the client, the ssh connection stays alive for around 15 minutes before ...
3
votes
2answers
534 views

When a server IP changes, do exising TCP (e.g. http/mysql) connections remain running

We have some PHP-FPM servers and when they need a database connection, they connect to an HAProxy server which selects them a database server to use and the connection opens. When we then want to ...
0
votes
1answer
110 views

How to send 0x80 byte to a tcp port using netcat or similar tool?

I'm trying to make a Memcached server respond as if I where using binary protocol. If possible just command line answers pls, no code spinet in any programming language.
3
votes
1answer
70 views

Is net.ipv4.vs.timeout_timewait used also for IPv6?

Does this setting for TCP net.ipv4.vs.timeout_timewait apply only to TCP connections established over IPv4 or does it also apply to TCP connections established over IPv6? I have found this for ...
-1
votes
1answer
49 views

TCP Server Memory management: #Connections Vs. #Requests

Given that, there is no theoretical limit to number of concurrent TCP connections a Windows 2008 server can handle. Only thing will happen is, with each connection there will be memory consumption in ...
0
votes
0answers
26 views

Security concerns regarding php://stdin

I'm using xinet.d and php://stdin to host a raw tcp-connnection, (following the excellent guide at http://gonzalo123.com/2010/05/23/building-network-services-with-php-and-xinetd/) I'm concerned with ...
0
votes
1answer
73 views

How to measure TCP connection time in Linux

I want to measure the overhead in creating a TCP connection. I know of many tools like hping and netperf, but they seem oriented at measuring latency. I want to know how long the 3-way handshake ...
1
vote
0answers
242 views

Improving TCP performance over a gigabit network lots of connections and high traffic for storage and streaming services

I have two servers, Both servers hardware Specification are Processor : Dual Processor RAM : over 128 G.B Hard disk : SSD Hard disk Outging Traffic bandwidth : 3 Gbps network cards speed : 10 Gbps ...
1
vote
2answers
640 views

Wireshark TCP Window Size Value

I am debugging an application with Wireshark and watching the TCP Window Size value shrink on one side of the communication. If the packet's TCP section shows a "Window size value: 1", does that mean ...
1
vote
1answer
178 views

iptables: unknown option “--dport”

When I try to run iptables -A control_in -p tcp --dport 22 -j ACCEPT I get the error message iptables v1.4.20: unknown option "--dport". Everything I've found on the internet and serverfault relating ...
-1
votes
3answers
132 views

What happen when I assign 2 IP on one NIC? [closed]

What happen when I assign 2 IP on one NIC? e.g. I have one physical NIC (eth0) and I assign on this interface 2 IPs from different network. e.g. auto eth0 iface eth0 inet static address ...
1
vote
0answers
55 views

Network flooded with LLC packet

Recently my network has been slow. From Tcpdump i found lot of frame with protocol LLC. A complete packet capture can been here tcpdump result Any hints on interpreting these packet?
1
vote
1answer
586 views

option http-server-close on HAProxy haproxy-1.5-dev19 will result in Connection: close header sent in response

I basically have the following issue: whenever I add option http-server-close to the haproxy config (either in frontend or backend section), haproxy will send a Connection: close header in the ...
-1
votes
2answers
204 views

block all packets in windows 7 (so nothing appears in wireshark)? Can anything locally installed do it?

is it possible to block all packets in windows 7, so that nothing appears in wireshark? I have tried choosing Block all for incoming. for outgoing, I see it has no block all option, just a block ...
0
votes
2answers
85 views

TCP Python Server

I have a question regarding connection reliability running a tcp server from an ec2 instance. We are currently serving mobile customers around the world from the Oregon region using a c3.4xl ec2 ...
0
votes
1answer
238 views

TCP Sequence & Acknowledgment numbers

I have looked through other questions on here involving the relevant topics, but I am still not clear on this. I have just been reading this explanation of TCP sequence & acknowledgment numbers. ...
0
votes
2answers
133 views

apache2 keepalive and opening a tcp connection

An IP packet contains a payload, such as HTTP information, which in turn contains html information. An IP packet is encapsulated into a TCP segment, which detects problems in transmission over ...
1
vote
3answers
164 views

Is TCP header the same as TCP segment?

So, is a TCP header actually the same thing as a TCP segment? I was reading this page, where it reads near the end that: Even though it might seem they are, in most cases, when referring to the ...
0
votes
1answer
182 views

Connect to sphinx on remote server

I recently moved sphinx onto the same server as our db so our architecture is: File Server that hosts our web app DB server w/ Sphinx instance (searchd) When I try to connect to sphinx at ...
0
votes
2answers
137 views

Debugging slow transfer rate from server

I'm trying to explain this as simple but documented as possible. This is not exclusive to this server or my current ISP. I've seen the same exact issue over the years while being with different ISPs ...
1
vote
1answer
119 views

Increase number of connections per socket

How do I increase the number of connections each socket can accept? I know that you can increase the total number of connections using: # sysctl kern.ipc.somaxconn=4096 But each connection is then ...
2
votes
1answer
270 views

TCP Window size increases drastically and sender don't send until the receive buffer is not empty

I have a download stream over TCP in an application (running on Win2k12). The problem is that the connection gets closed by the sender because it times out. I used wireshark to see what happens on ...
0
votes
2answers
98 views

FreeBSD Established Connections Maxing out at 300

We've previously had issues in our environment where it seemed we were reaching FreeBSDs max connection limit. We took action demonstrated by http://nginx.org/en/docs/freebsd_tuning.html and bumped up ...
0
votes
0answers
18 views

Debian as TCP-Server for Serial Port redirecting [duplicate]

I want to start a tcp listener on debian. One client should be able to connect and should get inputs of serial port in the tcp connection. And when the client sends data through the tcp socket the ...
0
votes
1answer
515 views

TCP Zero windows size and full windows size

The problem that we are facing is that some of the http connection have response time > 60s (about 5%). I discover that the problem should between the web server and loadbalancer. Here is my finding, ...
1
vote
0answers
318 views

What does “connections reset due to unexpected data” in netstat -s mean

I'm running a memcached server under heavy load from multiple web servers. While investigating some odd app level behaviour, we spotted that netstat -s on the memcached box was showing a lot of ...
2
votes
0answers
209 views

TCP connection timeouts that persist - listener queue backlog?

I have an app running on AIX 6.1 that has a single server process that listens for and polls tcp connections and simply forwards on messages to another process using an IPC message queue. It's been ...
0
votes
0answers
224 views

Keep doing TCP Retransmission with ACK, PSH

here is my situation: I got two servers, a loadbalancer (prowered by softlayer) and a web server running apache 2.2 and php 5.4. My web application only serve android mobile device. I was tested 2 set ...
0
votes
2answers
31 views

Distributed LAMP vs DB and Web Server same box

We have a very read heavy semantic web (RDF) application which is RHEL 5/Apache 2.2.3/Tomcat 6/Java 6 on one Server, and MySQL 5.1 on another. Apache and MySQL are backported Red Hat repo stuff, so ...
0
votes
0answers
72 views

Reproduce netperf TCP_RR test with NTttcp

The documentation of NTttcp being hard to find and to understand, how can I mimic the behavior of the TCP_RR netperf test with NTttcp?
0
votes
1answer
94 views

Linux tool to show connections/s?

Is there a tool/command to show connections per sec? I've tried a few iptraf and iftop but I can't see anything about connection rates.
1
vote
1answer
72 views

TCP timestamps field is in the future

I have a server sending TCP packets. I noticed, with wireshark, that my packets in the Timestamp optional field look like Timestamps: TSval 2552765291, TSecr 3858527953 The TSval is the value my ...
0
votes
0answers
204 views

iperf test in reverse direction gives different result

I used iperf to measure the max throughput for TCP connection between two ubuntu machines. Both the machines were directly connected be means of a 1Gbps cable. When I performed iperf tests i obtained ...
0
votes
1answer
139 views

Show real TCP/IP addresses behind Nginx environment

When i execute the command netstat -atun | awk '{print $5}' | cut -d: -f1 | sed -e '/^$/d' |sort | uniq -c | sort -n I see high number of connection assigned to server ip I want to see the real ...
-1
votes
1answer
64 views

Open file count keeps increasing forever

I'm experiencing issues with the number of files opened increasing over time. If I run my server for about few hours, it'll no more accept any connections. The limit was 1024. I've increased the limit ...
1
vote
1answer
661 views

Windows Server 2008 TCP connections limit

I run my own game server made in .net 4.5 on a Windows Web Server 2008 VPS. I have done some research on a problem I have. My app doesn't accept clients, if there are already 1000 clients connected. ...
8
votes
1answer
285 views

TCP packet being retransmitted 7 times when sysctl tcp_retries1 is set to 3 - why?

Ubuntu 12.04 I am trying to better understand how many times TCP will attempt to retransmit a packet when it does not receive confirmation the destination received it. After reading the tcp man page ...
2
votes
0answers
255 views

No response to some SYN packets when timestamps are enabled

I have a TCP server listening on a machine ("the server") running Ubuntu 12.04.3 (kernel 3.8.0-31-generic). It receives connections from 2 different client machines. Machine A is running Ubuntu ...
2
votes
3answers
372 views

Windows Server TCP sockets random disconnect: how to reproduce?

We rented 10 Windows servers from a large provider in Europe. They all work as expected. One server suddenly crashed and customer care found that both disks were broken. They replaced disks and also ...
1
vote
0answers
177 views

Linux MIPS box: ICMP (ping) works, but TCP does not - how to fix it?

I'm trying to set up MIPS Linux box network. Here is it's configuration: ~ # ifconfig eth0 Link encap:Ethernet HWaddr CC:5D:4E:FF:45:7F inet addr:192.168.0.2 Bcast:192.168.0.255 ...
1
vote
1answer
129 views

Low throughput on Debian + nginx/apache

On the same LAN/WAN I have a Windows server 2012 server running IIS 7.5 and a Debian (wheezy) server running Nginx 1.4.5. Both servers are connected to the same LAN/WAN. When I download a 10mb file ...
0
votes
0answers
118 views

How can I replay a TCP stream to my client

I need to do some validation testing of a new feed handler I have made. I have some pcap data that I captured from the production network and I would like to have my development feed handler connect ...
1
vote
1answer
62 views

TCP echo server security [closed]

I am setting up a Linux server similar to a TCP echo server and am wondering about security issues I should be concerned about. This will be a bare bones Centos/KDE server with no additional files ...
-6
votes
1answer
57 views

What is the incentive to operate a TCP/IP node? [closed]

I mean, why does anybody relay messages to other nodes? Why are these eleven good people below helping me send my bytes to their destination? traceroute to stackoverflow.com (198.252.206.140), ...
3
votes
1answer
51 views

Default TCP connection backlog value in Windows

Which is the default connection backlog value for TCP in Windows? I have tried to find it but no luck. Cheers
5
votes
6answers
568 views

How can I find the total number of TCP connections for a given port and period of time by IP?

On a Linux system there are plenty of methods for listing the current TCP connections for a given port by connecting IP but: how can I count the total number of connections to a port per source IP for ...