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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385 views

Test a server using MTR through TCP

Is it possible to use MTR over TCP? If not is there an alternative? I have done some research and I am not finding any way to do such a thing, so I'm wondering if anyone has had any experience with ...
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0answers
39 views

Apache process 100% with IPV4 TCP 10u

Today i got strange http ussage. All apache processes woks ok but after some time i found few processes stocked at 100% and they are like that long time. After i checked that process id at webmin ...
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2answers
193 views

Unable to POST/Upload files to a PHP page

I have a weird problem when I try to post contents or upload files by php to my server. After submitting the form it sleeps for a while then shows a page loading error. I tried different contents and ...
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vote
1answer
96 views

Is there a Windows utility to create a TCP server to server link?

I two systems that I need to connect, but both act as servers. The first is a scale controller that does not have the ability to open a connection before sending a weight. It will send weights if a ...
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votes
1answer
147 views

VMware - Host two VPS with same IP

I have: 1 Dedicated server, Windows server 2008. 2 Virtual machines inside the server. (VMware, Windows too) 1 example IP address: (0.0.0.1) 1 example IP address: (0.0.0.2) I need: 1 Dedicated ...
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0answers
44 views

Linux + OpenVPN + SNAT + Failure on client grab the reply to it's own generated traffic

Ok, I'm really desesperate I need to release an openvpn deploy to get rid of a dying server. On the subject: I installed OpenVPN with a routed interface (tun0) into a server with a public IP + 3 ...
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1answer
71 views

Fixed TCP payload Size [closed]

I have an aplication that need to have a fixed (516 byes) payload size in the TCP packet. The application itself can't be modified to adjust it settings, therefore i need to tune the TCP Buffer Size ...
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0answers
96 views

Strange dropped packets coming from port 8888 and with ACK or ACK+PSH set

Background During an incident on a small privative network (1 router/FW + 1 server) my server got accidentally exposed to the internet. Fortunately it was protected by it's own UFW to allow only 1 ...
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1answer
22 views

Information about SYN [closed]

I'm new to socket programming and i read that SYN packet can be created through a raw socket .But windows api doesn't allow the creation of a raw socket .I know that ICMP packet doesn't have any port ...
1
vote
1answer
386 views

How to edit TCP window size from iptables?

There is TCPMSS target to edit MSS value of connections (including forwarded). How to edit window size (for example, cap to some maximum value) by iptables rule? Expecting something like iptables ...
2
votes
1answer
658 views

How to capture retransmitted packet info with tcpdump?

TCP retransmission rate on a host are often a good indicator of network problems. How do I find out the source and destination IPs for the packets that are being retransmitted? For context, on hosts ...
3
votes
3answers
854 views

How to prevent TCP ZeroWindow on writing a large file to a Windows share?

I've been given access to a share on a Windows Server 2003 SP1 system (10.a.bbb.ccc) which is a file and printer server, and regularly large files get copied to that share. However, occasionally such ...
4
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1answer
2k views

Too many TCP connections causes disconnections

I have a game server which runs with TCP connections. Server disconnects users randomly. I think its related with TCP settings of server. In local development environment written code can handle ...
2
votes
3answers
5k views

Excessive 'TCP Dup ACK' & 'TCP Fast Retransmission' causing issues on network. What's causing this?

I'm getting excessive TCP Dup ACK and TCP Fast Retransmission on our network when I transfer files over the MetroEthernet link. The two sites are connected by one sonicwall router, so the sites are ...
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vote
1answer
1k views

What is msrpc needed for on a Windows 7 workstation

I just ran an nmap scan against our network, and many Windows 7 machines have several high ports listening with Microsoft Windows RPC. Example: Port Serv Process name 49152, msrpc [wininit.exe] ...
2
votes
1answer
552 views

Is ECN (Explicit Congestion Notification) turned on by default on Windows Server 2012?

In a company network I noticed that all examined Windows Server 2012 machines had ECN turned on: > netsh interface tcp show global TCP Global Parameters ...
-1
votes
1answer
39 views

Redis specific protocol

I was reading the redis documentation: http://redis.io/topics/quickstart And I come across this line "External programs talk to Redis using a TCP socket and a Redis specific protocol." TCP is the ...
0
votes
1answer
55 views

Port 1227 for a web form

A Panamanian government website has a form that is on port 1227. 1227 is used for network administration (DNS). Like most good companies, we blocks most non-standard ports, and before we open them ...
2
votes
1answer
257 views

Tomcat not getting data from TCP recv-Q, hanging

I have a program which is essentially a tomcat server with postgreSQL DB running on CentOS Linux 6.3. When a client submits a larger amount of data (~10MB) to the server, which should be received on ...
1
vote
1answer
207 views

Why does OS X spend one more packet to establish and close a TCP connection?

Linux spends 3 packets to establish a TCP connection and 3 packets to close it, as shown by the tcpdump capture # establishing TCP connection 22:37:09.150456 IP 127.0.0.1.49327 > 127.0.0.1.8000: ...
0
votes
1answer
358 views

How to increase nginx connections

I am facing the problem of nginx max connection issues. I am not able to increase max active connections(520) made by nginx. Some time it is using whole writing (516) operation connections. and due to ...
0
votes
1answer
71 views

Route TCP responses (ACK) through another interface

For reasons I can't go into, I am working with a strange network configuration. I have a one-way higher speed wireless link, and a slower bi-directional wireless link. There is a network interface ...
2
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0answers
269 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
255 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 ...
0
votes
1answer
521 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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votes
1answer
170 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
114 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
votes
1answer
343 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
votes
1answer
1k 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
140 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 ...
4
votes
1answer
586 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 ...
1
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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
191 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
votes
1answer
296 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 ...
2
votes
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
5k 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
votes
1answer
139 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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votes
1answer
63 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
243 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
274 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
vote
1answer
95 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
votes
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 ...
1
vote
0answers
109 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
votes
2answers
97 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 ...
0
votes
3answers
107 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
votes
1answer
165 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 ...
0
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1answer
181 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
votes
1answer
442 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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votes
1answer
48 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 ...
1
vote
1answer
100 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 ...