Tagged Questions

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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1answer
154 views

Problems with network after using a socks proxy

I was playing around with SSH and trying to route traffic through my laptop. In the end I succeeeded, however I seem to have messed up my network. I only used ssh and played around with both -D and -L ...
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1answer
1k views

How to send data to tcp server from command prompt [closed]

I am a java developer and quite aware of socket programming in java.I have a tcp server running my localmachine.I can write java codes for client and check communication between server and client.But ...
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1answer
1k views

Benchmark maximum number of TCP connections on Windows Server 2012

I am wrestling with deploying an application on Windows Server 2012. The problem is that after accepting about ~2000 TCP connections it fails to accept more. And I need much more. We have 8 cores, 16 ...
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2answers
1k views

Why are some tcp packets with the RST flag classified as new incoming connection?

While looking through my iptables log, I keep observing periodically incoming connections with the RESET flag being set from a few ip addresses within my ISP's network. This is a sample tcpdump on one ...
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2answers
442 views

eMule not connected

I'm using eMule v0.50a on Windows 7. After installation, I clicked 'connect' It is not connected. Please see the attached screenshot. It reads 'eD2K:Connecting, Kad:Connecting | Preparing' How can I ...
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0answers
130 views

Ethernet port on Linux machine not recognizing ethernet connection with embedded device

I have an atmel at91sam7x256 microcontroller that I would like to use for a TCP/IP communication. The very first step of my project is to be able to "ping" my board given its IP address. I have its IP ...
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1answer
34 views

Ethernet port re-transmission frequently

We have a laptop that uses its Ethernet port to connect to a device-local network, and wireless for Internet. Recently we installed Wireshark to diagnose some network problem. We found a lot of TCP ...
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2answers
273 views

Host local USB printer via port 9100 TCP

Is there a way to share a printer plugged into a PC running Windows 8.1 via USB over TCP port 9100? I have a piece of software here that only prints to such network printers and is not capable of ...
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0answers
45 views

Hiding port number from address.

I have centos 6.5 running some web apps. Currently due the following port forwarding rules, I am only able to access my public content using 127.0.0.1:8080/ Is there anyone to just use 127.0.0.1 ...
1
vote
1answer
107 views

How are ports and URI schemes handled by a tcp/ip server?

I am working with the lwip tcp/ip stack on an embedded device, and I'm trying to understand how it all works. I've been looking through the documentation and code, but I'm confused by how ports and ...
1
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1answer
138 views

TCP vs UDP. Sending data on a closed port

I try to understand differences between TCP and UDP packet on the error-checking. I know that UDP packets are connectionless and doesn't care that the packet will arrive the destination safely. And ...
0
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1answer
46 views

How can I turn on ECN for Mac OSX?

I'd like to run some networking tests with Mac OSX 10.8 and using the ECN option. However I cannot find any documentation on how to configure it. Does anybody know how to alter Mac OSX TCP networking ...
4
votes
1answer
4k views

For what does ssh use UDP?

Wile doing research I noticed that SSH both uses TCP and UDP. I completely understand the use of TCP, but UDP seems a bit strange. Why would I use an "unreliable" transport protocol with minimal ...
1
vote
1answer
123 views

Why HTTP response is split in 2 parts: header and body?

I'm trying to understand why a single HTTP response is split in 2 parts in the following setup: Requested resource is protected by HTTP Digest Authentication on server side. Communication is ...
0
votes
1answer
65 views

How to add code into the linux kernel?

I am studying how to analyse and evaluate the TCP/IP protocol stack of Linux. My goal is to study the performance of the tcp/ip protocol stack as a whole, to study the time cost of each layer and ...
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0answers
203 views

Iperf tests in reverse direction

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 ...
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0answers
121 views

How to use netperf on specific NIC port?

I have two servers, SERVER and CLIENT and each server has its own onboard 1 GbE ports, and its own NIC with a 10 GbE port. SERVER and CLIENT are interconnected on both a 1 GbE switch (administrative ...
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0answers
56 views

Setting/clearing packet's TCP flags with iptables

I know iptables can match packets with certain TCP flags using --tcp-flags. But how do I set or clear some flags on a matched IPv4 packet?
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0answers
85 views

why the ping doesn't get a reply?

I have an embedded board that has the CFE, a minimal loader. I have a host machine - linux FC16, where I am running a dhcpd server. My interface is p3p1. Here are the details of the ifcfg-p3p1. ...
0
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1answer
228 views

Restrict SSH server tunneling port

I have a SSH server running OpenSSH. I want to use it to setup a SOCKS server so that my friends in China can use it to access websites such as twitter. I want to enforce two restrictions: 1. no shell ...
0
votes
1answer
85 views

Simulate tcp window full on ubuntu

I have 2 ubuntu boxes. In between them is a firewall. I am trying to simulate tcp window full condition or in other words, I want the ubuntu server to send a tcp window full flag to client. Here are ...
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2answers
611 views

Windows Server 2012 cannot access web sites

I have a Windows Server 2012 that has gone a little crazy in the last 24 hours. It can't access any websites, internal to the network or on the web. I can ping google.ca for example and it resolves ...
4
votes
3answers
1k views

How to force a process transmit over UDP instead of TCP?

I 'm running an ffserver process on a Linux machine, in order to achieve video streaming via ffmpeg. However, there is a delay on video streaming. On ffserver configuration file I define Port 8090. ...
0
votes
1answer
76 views

DNS Resolver for Windows over TCP

I know that DNS uses UDP with Port 53 for DNS queries. However, at my place sometimes UDP requests are blocked and DNS fails. I know that there is protocol for DNS over TCP and many public DNS servers ...
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0answers
46 views

UDP causing problems with other connections

I have implemented a file transfer program on Windows 64-bit platform using winsock API. I am using a 1Gbps connection. When I transfer files using TCP protocol, I am getting only 320 Mbps. when I ...
0
votes
1answer
181 views

Session layer in OSI vs TCP/IP

I'm sort of confused here: According to several illustrations I've seen and material from Cisco the session layer from OSI is part of the application layer in TCP/IP. This makes no sense to me since ...
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2answers
53 views

TCP/IP minimal size

I am using a high level language on a PC to send a message via TCP/IP to a remote device which is an embedded device. I am sending relatively small messages (< 255 bytes). I must assume that there ...
4
votes
1answer
228 views

Why does writing IP addresses this alternate way work, and is there a practical use case for it? [duplicate]

Recently I saw an incorrectly typed telnet command, and I saw that "regular" numbers were interpreted to IP addresses. I tried this myself in Windows and the same behavior is shown there, so obviously ...
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2answers
67 views

Free official documentation for cables and models? [closed]

I've been looking through the ISO and IEEE sites for official documentation on the Open Systems Interconnection (OSI) model, TCP, and a range of cable standards (5/5e/6). However, other than on the ...
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votes
2answers
161 views

Is DNS query a UDP or TCP?

I know that when we first type an address on the URL and enter. The DNS query starts. I don't who initiates, but my guess is application will only initiate the DNS query. The DNS query already knows ...
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0answers
66 views

How do I drop a TCP packet matching a certain signature on windows (e.g. firewall-based)?

I am searching for a way to stop a TCP packet with a certain signature and connection from reaching an application. The packet may be dropped completely. The packet contains the byte signature [42, ...
0
votes
1answer
39 views

What impacts does RTT have on the behaviour of TCP?

How does round-trip time impact a TCP connection's behaviour? I know that the throughput of a connection with a high RTT is lower than the throughput of a connection with a low RTT but how does RTT ...
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0answers
37 views

TCP windows scaling in Windows 7 works only alternate times

I am running iperf TCP client in loop from another program. I am getting high and low throughput alternate times. I also tried to use fresh installed Win 7. This behaviour is not seen in Win XP and ...
0
votes
1answer
117 views

How to calculate TCP network speed

So basically this is an easy question, but not an easy answer. How do i calculate the download and upload speed in order to make program this in c#? I'm not sure how to take latency into account. I ...
1
vote
1answer
5k views

Communication possible between 192.168.0.x and 192.168.1.x?

I have a problem I encounter on a regular basis. I have an access point with a fixed 192.168.0.x IP address. My network is 192.168.1.x. The problem is when I plug the access point into my network, it ...
1
vote
1answer
96 views

Linux Kernel TCP socket functions

So I have been looking through the Linux Kernel v3.8.0-19-generic source code and I noticed that the proto struct, whose members are virtual functions for socket operations depending on the particular ...
0
votes
1answer
72 views

Throughput decreases after MTU 5000

I am trying to test throughput between two computers directly connected through 1 GbE and testing with iperf. I am getting a throughput around 980Mbps when MTU is between 5000 and 5050, however it ...
0
votes
1answer
102 views

Why TCP performance degrade with bidirectional traffic?

I've made a simple experiment on TCP transportation performance. The experiment is as follows: There are two machines, A and B, each installed with Ubuntu 12.04 Server. I've installed "iperf" on ...
1
vote
1answer
199 views

Is it possible to create a WiFi TCP socket between two computers in a LAN?

Here is our setup. The FEZ Cobra II (WiFi) Single Board Computer with a RS9110-N-11-22-04 WiFi module and running the .NETMF 4.2 The documentation says that: This allows for real "Socket" ...
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2answers
117 views

Can using UDP and OpenVPN lead to file corruption?

I know with TCP that it always checks your files to ensure nothing got fragmented or lost or destroyed. So if I use UDP for OpenVPN to download files or access an internal network, does that mean I ...
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2answers
76 views

Capture packets from other machines in local network

Is it possible to capture packets from other local machines on my Mac? They are primarily all wireless as well, if that makes it any easier.
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0answers
78 views

Delete Hung TCP Sessions with SNMP

What I am trying to do, and failing horribly, is to close a TCP connection... I am trying to do this via SNMP and the functionality that is provided in the TCP MIB. First, I look at all the ...
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0answers
16 views

How to keep socket visible after closing the connection?

Is it possible to configure Linux to keep a tcp connection visible for netstat/lsof after being closed? (doesn't matter the connection state). I need to detect it with netstat/lsof but if the ...
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0answers
114 views

Windows 7 / PuTTY drop IPv6 TCP connections on brief outages

This is an IPv6-version of the following question: Why Windows 7 / PuTTY drop TCP connections even on very brief outages? After moving from IPv4 to IPv6, I've noticed that my IPv6 connections would ...
2
votes
1answer
1k views

What's up with port 8080 on my OSX box?

I thought a web server process I brought up was listening on localhost:8080, and tried to connect to it, but kept getting connection reset errors. As it turns out, I was mistaken and my process was ...
0
votes
0answers
375 views

how to kill a tcp connection in solaris operating system?

A client program connects to my server program written in JAVA via TCP connection (ServerSocket). I want to close the TCP connection between these two programs with a Solaris command or tool for ...
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0answers
18 views

TCP behavior in microsoft products

What happens when a TCP SYN segment is received on a closed port? Does windows send a RST or it just ignores it?
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0answers
107 views

No response received from github ssh randomly

My git pull started to stop working randomly with this error $ git pull ssh: connect to host github.com port 22: Connection timed out fatal: The remote end hung up unexpectedly I tried debugging ...
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0answers
172 views

TCP/IP resets (Linux, SSH, RDP, ADSL router)

I have an ADSL router (model Pirelli DR A226G) that seems to cause dropped tcp/ip connections (not ADSL connection per se). I have tracked it using Wireshark and captured a few cases and they always ...
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2answers
102 views

Does TCP verify data all at once or as a packet by packet verification?

I know that TCP uses verification to ensure accuracy of data by sending to the server. My question is does it verify everything at once or as it comes in? Quick Example: Let's say I am loading the ...