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Questions tagged [tcp-ip]

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Unity Not Accessing Networking Port

I have an application I made in Unity which I know works on a Windows machine. I'm building it from the same project on my Ubuntu machine and it does not seem to be connecting. It should be opening ...
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0answers
14 views

Forwarding Traffic From One Port to Another and Vice Versa

The goal: Have process A send messages to process B and vice versa via TCP (I'm using ROSBridge). The problem: Only one process can use a port at a time The solution (?): Have process A use port ...
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Amount of UDP or TCP packets for set up time

is there a way to count packets throught Command line for last hour? Example: Right now is 15:00 and I would like to now amount of packets from 14:00 to 15:00. Thanks for help. :-)
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33 views

Sending a custom TCP packet

I am building a program that extracts transport layer data from packets, I want to test it but I couldn't find a way to specify TCP flags using netcat. Is there a tool that does this for Linux, or is ...
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Ubu 18.04 scanner TCP samsung C460FW (Error during device I/O)

Passing to ubuntu 18.04 last week, my Samsung C460FW connected with a network cable (not USB cause of distance) does not scan anymore: scanimage -L is OK device `xerox_mfp:tcp 192.168.13.50' is a ...
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1answer
66 views

How to permanently close a port?

I tried first adding a firewall rule sudo ufw deny 22 $ sudo ufw status To Action From -- ------ ---- 22 DENY ...
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0answers
64 views

Cannot run PostgreSQL on port 5432

When I try to start PostgreSQL on port 5432, it fails saying it can't connect to the tcp address. However, after changing the config to port 5433, it starts just fine. waiting for server to start.......
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32 views

keep receiving SYN_SENT on my server

can anyone explain this ? one is from a chinese ip the other a ip by Digital Ocean. I been track them and they keep sending this SYN_SENT on all non used ports The server is a public dns so they are ...
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1answer
113 views

Ubuntu 18.04 LTS: Slow down on localhost after recent update

I have been developing a network enabled application and been testing it on 127.0.0.1 (localhost). The application is completely memory bound, i.e. it never touches the hard disk. The procedure of ...
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0answers
38 views

How to configure port for external access?

I need to access software from another machine in PORT 3000, but I can not do it for the IP of the machine, only by localhost. erick@erickmordecai:~$ ifconfig enp3s0: flags=4163<UP,BROADCAST,...
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28 views

How to enable Debug logging for TCP stack in Ubuntu

We are facing an issue with Ubuntu server, what is happening is that any new TCP connection with the first SYN packet is getting rejected by our Ubuntu server with an immediate RESET, Wire shark does ...
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61 views

FIN/ACK delayed in apache and Ubuntu 18.04

After installing a server with Ubuntu 18.04 and apache a new behavior is seen on Connection: Close HTTP requests The HTTP answer is always fast, but some times the FIN/ACK close of the connection is ...
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1answer
179 views

Unable to access Docker NGINX on 18.04 LTS

I'm running Ubuntu 18.04 LTS. > docker-version Docker version 18.06.0-ce, build 0ffa825 I run: > docker run --name my-nginx-1 -P -d nginx > docker port my-nginx-1 80/tcp -> 0.0.0.0:...
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0answers
98 views

Bluetooth PAN: permanent piconet

I need to create a PAN with BlueZ 5, to form a piconet (the most basic Bluetooth network) and send TCP/IP traffic on it. I must not share internet access, it should be a simple private PAN between the ...
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0answers
128 views

iperf3 shows that udp with set bandwidth is still x2 slower than tcp

I opened iperf3 server on host 192.168.1.105: iperf3 -sV Then client on TCP on same host: iperf3 -c 192.168.1.105 -4b 10G -P 2 -n 10G -w 1M Results are: - - - - - - - - - - - - - - - - - - - - - -...
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0answers
173 views

Changing TCP ACK delay

TCP ACK is described here: https://en.wikipedia.org/wiki/TCP_delayed_acknowledgment I know very little about this - I just learned about it via this ticket that I filed with Node.js: https://github....
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150 views

How to manually allow external access to ports 14141 TCP and UDP in linux 16.04?

I require external access to ports 14141 TCP and UDP. I need to manually allow access to these ports. I am an absolute beginner. Detailed steps would be highly appreciated. Thanks!
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30 views

Specify Maximum TCP payload length for packets

I want my TCP packets to have 300 bytes payload atmost. In the other words, packets with more than 300 bytes must chunked to smaller 300 bytes packets. Is there any way to do that? I've tried to set ...
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37 views

How to turn off TCP ISN randomizationo and port number randomization

I setup two Ubuntu 16.04 VMs to do some network experiment. The question is: How to turn off TCP ISN randomizationo and port number randomization? For example, every time when I establish new ...
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2answers
74 views

Why ip addresses on local network [closed]

My question is more "philosophical" than practical. Since all hosts on a Ethernet local network NIC have a MAC address that identifies them uniquely, why does the dhcp service assigns them an ip ...
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0answers
391 views

tcp_probe function not implemented

Good day! I was trying to load the module "tcp_probe" when I got the following error "modprobe: ERROR: could not insert 'tcp_probe': Function not implemented" for reference, my kernel is 4.15.7 and ...
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0answers
170 views

nslookup working fine but ruby http call throwing error - getaddrinfo: Try again (SocketError)

nslookup and dig are resolving the address but ruby program throwing error. here is the stack trace 10: from /usr/local/bundle/gems/rest-client-2.0.2/lib/restclient.rb:67:in `get' 9: from /usr/...
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42 views

How to config tcpProxy to do that

In my case there is: Client (need to open testtt.com for example) DNS server ( configured when a client ask about testtt.com to go to a tcpProxy server 1.1.1.2 but the real ip for this website is 1.1....
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181 views

Socat symlink - Can't open COM

I installed socat and set up a virtual serial port over TCP:IP to communicate to an RS232 device remotely socat pty,link=/dev/virtualcom0,raw,b115200,user=master tcp:192.101.1.198:4000 I can send ...
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115 views

Virtual COM port over TCP

I have a rCell 500 router with a serial port COM. On this router, I have set up a server TCP (192.101.1.198:4001) who transmit the serial port data. On windows with a software, I successfully ...
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33 views

TCP/IP stack location In ubuntu kernel directory? [duplicate]

Basically I want to see/edit linux TCP/IP Stack. I Downloaded The source of Ubuntu from kernel.org using command links kernel.org And the file I got is linux-4.14.15.tar.xz. So I extracted it with ...
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0answers
184 views

ethernet not working - xubuntu

Here is the result of ifconfig eth1 Link encap:Ethernet HWaddr 08:2e:5f:86:46:c5 inet6 addr: fe80::a2e:5fff:fe86:46c5/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:...
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0answers
105 views

hping3 Sending Different Seq and Ack value than Specified?

To be precise. I am trying to perform a session hijacking attack. This is what I basically Am doing: I have kali-Linux (as server), Windows 10 as client and an Ubuntu as my Attacking OS. Server ...
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2answers
468 views

Connect two PCs via LAN

One PC is running Windows 7, and another one is running GNU/Linux 16.04. My goal is to transfer 75GB big data from one to the other.I have ethernet cable and I have already tried creating LAN(TCP/IP ...
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2answers
95 views

Wrap tcp listener script so that it uses a sock file instead

I have a program when run, starts listing on on port 12345 $ ./cool_script.pl My linux administrator says it's against the policy to open ports. He says I'm allowed to use ~/cool_script.sock (unix ...
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1answer
399 views

how to connect multiple clients on server

nc -l -vv -p 7795 This is the command for listen the port But i can connect only one client by using(nc localhost 7795) to the port,tell me how to connect multiple client to the port 7795
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2answers
5k views

Ubuntu 17.10 VPN

Enabling VPN connection from the Network manager automatically add's IPv6 address to DHCP Wired connection even if it's disabled on the settings. This causes the VPN to leak on all DNS address queries ...
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0answers
27 views

Confusion over limit in iptables rule

Let's say I wanted to apply some limits to HTTP traffic. Specifically, would I use -j ACCEPT or -j REJECT and how would I test that it's working correctly? (numbers are made up) iptables -I INPUT -p ...
2
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1answer
578 views

How to Reduce Buffer Bloat on an Ubuntu Based Router

I had an old Dell Optiplex 790 (added dual Intel PCI-E gigabit NIC) sitting around that I decided to make into a router using Ubuntu 16.04 and the guide found here https://arstechnica.com/gadgets/2016/...
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1answer
1k views

Postgresql refusing TCP/IP connection after ubuntu restart

This one has me baffled. I rebooted my ubuntu server and now I try to connect with pgadmin and I get the following: could not connect to server: Connection timed out (0x0000274C/10060) Is the server ...
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0answers
25 views

kernel 4.9.20-040920-generic with a TCP ACK number incorrect issue

hi all we use tcpdump to capture packets from a TCP receiver site. As the pic shows, TCP ACK number is incorrect: The kernel we are using is 4.9.20-040920-generic, is this a bug of this kernel ...
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1answer
402 views

What user permission is required to listen to port 8080

I'm trying to run Cuberite under its own username, cuberite. However, when I sudo -u cuberite ./Cuberite I'm unable to connect to it with my web browser: $ sudo lsof -i :8080 COMMAND PID USER ...
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1answer
343 views

Why can't I ping the IPv6 loopback in my Vagrant Box?

I watched a video tutorial about the loopback address. I learned that 127.0.0.1 is the IPv4 loopback address, localhost also points to IPv4 loopback address, and ::1 is the IPv6 loopback address. ...
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1answer
415 views

How to configure iptables to work with tcpcrypt?

Background OS: Ubuntu 16.04 x64 running on VirtualBox I am a developer with minimal Ubuntu/Linux knowledge and have been assigned to a project where the goal is to utilize tcpcrypt when ...
1
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1answer
214 views

Use nmap scan specific ports to see which IP addresses are running any of those

I have a question to write a script using nmap to look at TCP ports across the entire network to identify which IP addresses are running any of those services. Sorry my english is not good.
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1answer
2k views

sysctl: cannot stat /proc.sys/net/ipv4/tcp_frto_response

I'm trying to tune some tcp parameters to enhance the performance of the wireless network I have. One of those system parameters are tcp_frto and tcp_frto_response. The first value I was able to read ...
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0answers
268 views

I need a multi-server simulator to test an application [closed]

I want to test an application written on python 2.7 that sends data to two servers on two different devices by ethernet. Therefore I need an application that simulates these servers so I can see if ...
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2answers
130 views

TCP communication with robotic arm -Destination Host Unreachable-

I'm trying to communicate with a robotic arm via TCP/IP communcation. It works well on windows but when i try it on linux matlab i cannot connect to arm. Matlab tries to connect again and again ...
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0answers
533 views

Rsyslog losing message when sending via TCP

I was trying to build a custom Syslog server on the Windows platform, which I, for a start, am implementing a basic TCP listener (server). I encountered problem and I have asked this on StackOverflow: ...
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1answer
646 views

How to use wireless(wlan0) and wired (eth0) at the same time?

I am working with an embedded system in my lab and to remotely access the board, I have given a static IP to the board on Ethernet connection. The problem is - due to security reasons Ethernet ...
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0answers
228 views

How to enlarge network buffer size in Ubuntu?

How to enlarge network buffer size in Ubuntu? I want to make some file transfers with low latency and I want to try it increasing the network buffer size. How could I do it?
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1answer
560 views

TCP/IP stack implementing files in ubuntu [closed]

TCP/IP stack is implemented in ubuntu. Where are these files located in ubuntu 14.04.
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1answer
254 views

Set System Variable in Ubuntu

I install Multipath TCP kernel and try to make it work. I don't know how to set the system variable as explained in http://multipath-tcp.org/pmwiki.php/Users/ConfigureMPTCP. Using Ubuntu 15.04, for ...
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1answer
235 views

TCP or Telnet server for Ubuntu

I can use telnet to connect to a telnet server simply by typing: 'telnet localhost', whereas localhost can be replaced with any desired IP-Address. But now I want to do something different and I have ...
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1answer
2k views

How can I change Maximum segment lifetime in Ubuntu 14.04

How can I change maximum segment lifetime in Ubuntu 14.04? there is no net.inet.tcp.msl there The problem is that I need my TCPsockets to live more than 240 seconds..