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.

learn more… | top users | synonyms

2
votes
3answers
336 views

Is the same port acting as both client and server?

i find something strange in this netstat output. the output is taken using netstat -a -n -o -p TCP command on win 7. Proto Local Address Foreign Address State PID TCP ...
1
vote
0answers
679 views

connect to a serial device via TCP socket

My setup is this: serial device ttyUSB0 connected to laptop A software that opens TCP socket to listen and write to, also runs on laptop A (linux) My goal is to pipe data from/to serial device ...
2
votes
0answers
521 views

MySQL crashes when connecting from localhost with tcp (UNIX sockets work)

I have Ubuntu 12.04 running MySQL server 5.5.24. I can connect with mysql --user root -p. status shows me : ... Connection: Localhost via UNIX socket ... When I try to connect with mysql --host ...
1
vote
2answers
9k views

what is type of ICMP packets? TCP or UDP

ping packets is a type of ICMP packets.Is there any relation between ICMP with TCP.In other can we guaranty their arrival in the network I want to know ICMP packets in the network is tcp or udp or ...
-5
votes
2answers
173 views

Is there a way to pause/resume particular TCP connection?

I'm playing online game that matches me against random players. I found out that when I unplug my Ethernet cable, I have a minute to decide do I want this match to count. If things go wrong, I just ...
2
votes
1answer
126 views

How to monitor TCP and UDP port changes

I am running software on a server that may be turning off some ports and need to find out what it is. I have the ports I need to check. I just need to find out what is turning them off. How can I ...
3
votes
2answers
867 views

How to prove provider is blocking incoming traffic on some ports?

I hope this is not too much focused on home networks, because that's where I hit the problem, but I think it may be of general interest nonetheless. I have a cable connection (Cisco EPC3208) and a ...
2
votes
2answers
4k views

Why is my UDP so slow?

I'm using Iperf on two VMs and when using TCP I find the performance is as follows: notroot@ubuntu:~$ iperf -s ------------------------------------------------------------ Server listening on ...
3
votes
1answer
3k views

Redirect serial com to tcp port

I would like to know if exists some utility that connects to serial port and redirect input and output to a tcp port. I need this for a Java application, I need to write and read to a serial port but ...
3
votes
3answers
2k views

Can't connect to SSH server using WAN IP address [duplicate]

I have an SSH server behind a NAT router. Machines on the same (NAT'd) network as the SSH server can only connect to the SSH server using the LAN IP, not the WAN IP. Why? My network looks like this: ...
2
votes
1answer
505 views

Using tcpdump on displayed TCP data

If sudo tcpdump -i eth0 -X gives me tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes ...
0
votes
0answers
440 views

Ubuntu openVPN TCP no internet, UDP works. Win7 works on both TCP/UDP with same settings

I've recently purchased a VPN service which I'm connecting to with openVPN. On Windows 7 I can connect on both UDP and TCP settings, but when I'm trying the same thing on Ubuntu 13.04, it gives me ...
0
votes
0answers
39 views

I think that someone else is entering my computer for long, sth like back orifice. I then got TCPView. Now, what do I do?

I got some variations of the name of my own computer going on in TCPView, for instance. I wonder whether that means another computer, like in one instance the name appears in capital letters, in ...
1
vote
1answer
800 views

Connection stays alive but endpoint is dead?

Does anyone have an idea what would cause a TCP connection (client side) to stay in the ESTABLISHED state for about 24 hours, even though the server was restarted? The client process stays on the ...
0
votes
1answer
259 views

Using and testing UDP data over the internet [duplicate]

I have a GSM modem that sends data via UDP (it appears) I have configured it to send all data to my public IP address over the internet but no data is arriving at my end so I need to troubleshoot. I ...
1
vote
1answer
429 views

Server response in TCP 3-way handshake

A server normally responds with SYN ACK in a 3-way handshake. What would happen if it just responded with ACK?
0
votes
2answers
437 views

Any free program for binary TCP communication?

I have a TCP server listening on a localhost's port so I need a software that can be used to establish a TCP connection to the server and then send binary data, not ASCII. For example, I want to send ...
1
vote
2answers
123 views

Does TCP care about the incoming port?

Does TCP care if the port changes on a SYN/ACK that comes back compared to the destination port asked for? I.E. If i have a port forward turning 80 into 8080, and the client sends a SYN on 80 and ...
0
votes
1answer
63 views

TCP freeze problems

I have a server which I am testing for functionality (not load, not stress) with tsung. 50 users / second, 100 total users. Judging from tsung (tsung is the testing framework) graphs, there TCP ...
0
votes
1answer
97 views

Are all internet file downloads using FTP protocol?

I heard, FTP is used to transfer files over a network. Also heard that it uses TCP port 20 and 21. So TCP is connection oriented. We have acknowledgments. If the transmission is lost, we should be ...
0
votes
4answers
909 views

Can't host any server, ports blocked from external requests by accessible via LAN

I am running a Minecraft server hosted at TCP 25565 which I can access via LAN, but cannot be reached externally. I am not using any router and it is connected to an RG-Box Allied Telesis ...
0
votes
1answer
104 views

How can I fire many HTTP requests using a single TCP connection?

I would like to know if there is a way to open a single TCP connection to a server and request several pages over HTTP on that connection. Is there a way to do this using common Linux client tools?
1
vote
1answer
74 views

Why is it possible to continue working in a ssh session after a network disruption?

What enables the Secure Shell client and server to resume communication after one or several network interfaces in the communication path between them is shut down and re-appears some moments later? ...
0
votes
1answer
84 views

Simple program to turn a server into a client and vice-versa?

What would be a simple to use program for Windows that would do the following: Computer A unknown TCP client wants to connect to computer B's unknown TCP server. Both are behind a NAT. Computer A ...
0
votes
1answer
43 views

Filter outgoing connections but allow incoming

I a computer on my local network that I want to have accessible from any computer on the local network as well as from the internet, but I don't want it to be able to connect to other computers. I ...
0
votes
2answers
227 views

Monitor Application Network Activity

I use TCPlogView to see all tcp activity of a software. for example: An app (sample.exe) downloads this file in background: google.com/dl/sample.txt when I track it with a TCP software I see this: ...
1
vote
2answers
528 views

What is “armtech daemon”?

I ran a netstap -p tcp on my machine (A macbook) and noticed a number of entries for something called localhost.armtechdaemo. Searching the web doesn't really give me anything useful. Does anyone ...
0
votes
1answer
874 views

have tcpdump show the 'conversation' as i would get from wireshark?

Is it possible to get the same output i would get from: tcpdump port 80 -w log.pcap wireshark log.pcap in wireshark Analyze > Follow TCP Stream and then in the bottom drop down Entire ...
1
vote
0answers
193 views

Load TCP New Reno protocol

I am doing some test of the congestion control protocols and I cannot find how to load the protocol New Reno. I loaded a lot of protocols like Reno, Vegas, Hybla, Bic, Cubic, etc using the sysctl ...
2
votes
2answers
88 views

Is it possible to suspend a socket (SSH session, specifically) to switch network devices?

When resuming a tmux workspace on my laptop, I regularly have to decide between the wired and WiFi connection. Ethernet has very low latency, but forces me to reconnect any time the laptop is moved. ...
2
votes
1answer
4k views

Wireshark - How do i filter the TCP[RST] packet?

I am looking for filter out the TCP[RST] packets on wireshark. I have tried tcp.analysis.flag but it didn't help.
0
votes
0answers
322 views

Firewall is blocking echo request on port 7 (TCP)

I have an app which needs to receive a message back from the server. With the firewall on, I do not get the message back. If I turn off the firewall I get the request back. I have added some rules ...
0
votes
3answers
1k views

How to monitor TCP connections over time

I have an application which is a windows service. It accesses a number of other services using TCP/IP. E.g. sql server databases, informix databases, mail servers, etc. For instance it will also ...
1
vote
1answer
598 views

How does a proxy know where to forward the requests to?

When a proxy receives a connection how does the proxy know where to forward the request to? For example in Java we can set a system property for proxy. So we set the IP of the proxy and the request is ...
1
vote
3answers
1k views

Network Traffic per process/application windows

I know that there are plenty of applications to do this (like procexplorer) but is there anyway to access the winapi (what method/reference is used) to retrieve the network traffic (TCP, UDP, etc) per ...
1
vote
2answers
199 views

Data corruption after upgrading broadband speed and modem/router

I'm using an ISP called Fibertel in Argentina, and I recently upgraded my connection to 30 down/3 up. With this change came a new modem+router: the Motorola SBG 6580. Before I had something like 1 ...
3
votes
4answers
89 views

TCP/IP on the transport level

I'm trying to understand what happens when I send a packet using a socket on the transport level. Do all packets which leave my computer go first to a geographical location designated by my ISP? Then ...
5
votes
1answer
414 views

What type of TCP connections are counted?

In Windows 7's Resource Monitor, in the TCP Connections graph at the top right -- how are those connections being counted? Does a "listening" state count, for example? Does it matter what state a ...
2
votes
2answers
5k views

TCP: Maximum number of connections (client and server)

In the description of TCP in the Wikipedia, it is stated that The number of sessions in the server side is limited only by memory and can grow as new connections arrive, but the client must ...
0
votes
1answer
340 views

why TCP window scale values (scaling factor) are different in different hosts?

why TCP window scale values (scaling factor) are different in different hosts? why not make this value the same on all hosts? in theory, this value is between 0-14. what is the practical range for ...
3
votes
2answers
607 views

Are there any requirements for the sequence numbers on TCP Reset packets?

If there is a TCP connection between TCP program A and B, and its source IP address/port and destination IP address/port are known by an attacker, now the attacker wants to send a TCP Reset packet to ...
4
votes
2answers
11k views

what is TCP Half Open Connection and TCP half closed connection

I am trying to understand what is the difference between TCP Half Open Connection and TCP Half closed connection can any one tell what exactly are they?
0
votes
1answer
161 views

TCP video streaming: TCP throughput(rate) and RTT

we know that a rough estimation of TCP rate is: WINDOW/RTT, where WINDOW is the min(CWIN, RWIN), CWIN is the congestion window size of the sender, while RWIN is the receiving window. nowadays, the ...
1
vote
2answers
491 views

TCP SYN does not reach TCP server

I have a TCP server listening on 10.10.10.101, port 2000, running on a Windows 7 machine. Below is the corresponding output line for the command netstat -aon: TCP 10.10.10.101:2000 0.0.0.0:0 ...
5
votes
1answer
232 views

Find processes listening on the wildcard address in `lsof`

Using lsof, I can find all of the processes with a TCP socket listening for connections: lsof -Pni -sTCP:LISTEN e.g.: COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME cupsd 662 ...
1
vote
2answers
1k views

Why does TCP sometimes not acknowledge the packets it receives?

I use firefox to visit a web server running on a computer on my LAN. I notice that sometimes TCP doesn't acknowledge the packets it receives. For example, in the following captured packets: ...
5
votes
3answers
9k views

How exactly does a proxy work?

If I want to connect to say, IP 100.100.100.100, Port 80, my computer will send a tcp packet with this adress into the wire. Now If I use a proxy server say, 200.200.200.200 Port 8080 (such kind of ...
2
votes
2answers
6k views

TCP Slow start and congestion control, and how to modify them

I'm trying to change the behavior of the tcp slow start protocol on a CentOS5 box (uname -r => 2.6.18-238.12.1.el5). I have read that the following command will change my icwnd to 8: ip route change ...
1
vote
3answers
2k views

Open TCP port in Windows 7 and read incoming data, what program to use?

I have an external device which can connect over GPRS to the Internet using a SIM card and I want to see what data it sends. I can program it to use my computer as a server and then use a program to ...
0
votes
1answer
779 views

about combinations of TCP flags

TCP FIN packet, ACK flag is always set? In TCP tear-down phase, there are usually 4 packets: FIN/ACK, ACK, FIN/ACK, ACK. Is it possible some of these packets may not be sent by a TCP peer? When there ...