Questions tagged [tcp-ip]
The tcp-ip tag has no usage guidance.
64
questions
0
votes
0
answers
116
views
Multiple connections to the same serial port
I'm trying to connect to clients to the same serial port.
The serial port is shared over the network with TCP on port 1234.
I tried with socat tcp-listen:1234,reuseaddr,fork tcp:remote-ip:1234 but ...
- 21
0
votes
1
answer
345
views
Sending Serial data over TCP/IP in command line
I've wracked my brain over this and been through several dozen help files and tutorials, and just cannot figure how to properly do this in Linux.
The situation is that I need to send serial text to a ...
0
votes
0
answers
164
views
Slow internet connection How to investigate?
About 2 days ago the internet on my laptop (dell vostro 3550/Ubuntu 22.04) suddenly became pretty slow. The internet is working fine when I connect from an Android phone.
So, how can I investigate the ...
0
votes
0
answers
297
views
Connection refused on open TCP port
Server is listening on TCP port 10000 on two reachable addresses-
root@localhost:~# netstat -tulpan | grep 10000
tcp 0 0 172.30.83.74:10000 0.0.0.0:* LISTEN 29009/...
- 103
0
votes
0
answers
45
views
tcp6 timewait is consistently higher after upgraded from Ubuntu 18.04 to 22.04
Our service just migrated from Ubuntu 18.04 to 22.04 instance. But we found out that TCP6 connection with time_wait state increased significantly, in Ubuntu 22.04 they are around ~200 connections, ...
- 121
2
votes
1
answer
332
views
I need a simple TCP load balancer in Ubuntu
I would like to create a load balancer for RDP connections only, that’s one TCP port only and would like to avoid anything more complex like Nginx.
I don’t need cache, or anything else, just take an ...
- 21
2
votes
1
answer
897
views
Why does apache2 not show on tcp4 ports although it is listening on both tcp4 and tcp6 ports by default?
Why does apache2 not show on tcp4 ports although apache2 is listening on both tcp4 and tcp6 ports by default ?
$ alias nocomment
alias nocomment='egrep -v "^(\s*#|$)"'
$ nocomment /etc/...
- 2,171
1
vote
1
answer
571
views
TCP available congestion control - reno or new reno?
I use Ubuntu 20.04.
sysctl net.ipv4.tcp_available_congestion_control
returns:
net.ipv4.tcp_available_congestion_control = reno cubic
I am not sure whether reno is in fact new-reno.
I see fast ...
- 13
0
votes
0
answers
544
views
can't connect some IP addresses via 'telnet 217.168.180.104 18000' ; telnet: Unable to connect to remote host: Connection refused
I can't connect some IP addresses via 'telnet 217.168.180.104 18000' ; gives below errors:
telnet: Unable to connect to remote host: Connection refused..socket connect error.
ufw desabled, the ...
- 1
0
votes
1
answer
635
views
Creating a TCP socket
I have been a Mac for a number of years and I am hoping to become a Penguin Fan for the purposes of technology development.
I am in the process of developing connected technology which requires TCP ...
1
vote
0
answers
53
views
TLS handshake decryption
I have an offline Pcap file with a lot of data from many different protocols. I would like to decrypt the Transmission Control Protocol data from the 3-way handshake.
Transmission Control Protocol ...
- 11
-1
votes
1
answer
130
views
Is there any way to resctict telnet to communicate with C++ TCP server [closed]
I have a TCP server developed in C++. Currently, it's allowing all connections in the XML bytes length protocol. Due to some security reasons, is there any way to restrict access from the client using ...
- 3
3
votes
0
answers
796
views
What do I need to tweak to avoid TCP duplicate/out of order ACKs during file upload from some computers?
I'm seeing an issue with a specific combination of circumstances that causes TCP duplicate ACKs to be sent. This happens with a service hosted on Ubuntu Server 20.04.
I have a web service that, among ...
0
votes
1
answer
50
views
Is it possible for a bug in the source code ports of the network(TCP/IP)?
That may not be a logical question.
But I would like to understand this.
Any service that provides services on the Internet
Has a set of specifications and ports based on standards and tasks.
To ...
0
votes
0
answers
621
views
I am able to ping to my machine IP but getting site unreachable on browser
My mobile and Desktop both are connected to a router.
When I am making a python server from Desktop on 0.0.0.0 on port 6500 I am able to ping it from my mobile (using Termux) but not able to access ...
1
vote
0
answers
871
views
Delphi Indy TCP Socket Server Sometimes Freeze and What is the limit
I made TCP Socket Server application.
Embedded GSM module devices are connected with TCP/IP protocol on GSM Line and send about 140 bytes of data in per 1 minute. I parse this 140 bytes of data and ...
- 11
0
votes
1
answer
90
views
Could not connect when port forwarding?
I have a server that I'd like to be accessible from outside my home network. On my router, I am forwarding port 8978 from the server, and my server is running a php script and listening to port 8978.
...
6
votes
1
answer
2k
views
TCP send performance issue on 18.04
I am playing around with Ubuntu 18.04 and I'm noticing TCP performance regression that prevents me from upgrading my current running servers since they are very latency-sensitive.
For my particular ...
- 111
4
votes
1
answer
386
views
Server stops accepting connections after ~120,000 active on 18.04.3
I'm running a type of perf test where I have a simple TCP server with 4 IP addresses that is listening on a port and getting connections from several other computers on the local network. Everything ...
- 61
2
votes
1
answer
416
views
How to disable rhythmbox port 3689?
I installed rhythmbox on Ubuntu 18.04 LTS, since VLC several times hanged/crashed the GUI during video play.
But by suprise rhythmbox is listening on the public IP (not localhost) on port 3689, ...
- 23
10
votes
1
answer
21k
views
Redirect an external IP to localhost?
Is it possible to redirect all calls to an external IP on internet, to localhost (without use of hosts)?
I have an old application and I don't have the source code and this application try to connect ...
- 1,145
1
vote
2
answers
2k
views
tcp_probe could not insert 'tcp_probe'
I'm Trying to Work with tcp_Probe, but I became this error:
ERROR: could not insert 'tcp_probe': Function not implemented
my kernel version is : 4.15.0-55-generic Ubuntu
I have seen, that many ...
- 11
0
votes
0
answers
39
views
TCP session is not timing out even when link is shut
Distributor ID: Ubuntu
Description: Ubuntu 14.04
Release: 14.04
Codename: trusty
Sequence of steps:
Using nc -l 9999 started listening on Ubuntu VM.
Ran nc client is on another Linux VM to ...
- 1
0
votes
1
answer
51
views
How to make an outgtoing TCP connection through specified netwrok interface?
Is there a way to implement in C program a next feature: it's need to making outgoing TCP connections through specified network interface? as example:
eth0 - 172.16.0.1
eth1 - 192.168.1.1
In some ...
0
votes
1
answer
828
views
Ubuntu 18.04.1 LTS keeps killing my Ethernet connection when it cannot find an Internet connection
I have a device (a nuclear radiation detector, specifically) that streams binary data over a TCP/IP connection. To stream the data, I simply connect it to my laptop via Ethernet and set the wired ...
1
vote
1
answer
112
views
Ubuntu Networking to Allow Connecting to Host Machine
I have a Unity project and a ROSBridge host. When I run the Unity project from a windows machine, it can connect to the ROSBridge as hosted by two different Ubuntu machines. Putting the Unity project ...
- 71
0
votes
1
answer
452
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 ...
- 71
0
votes
0
answers
697
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 ...
- 41
0
votes
1
answer
2k
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 ...
- 2,947
0
votes
0
answers
3k
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.......
- 101
0
votes
0
answers
670
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 ...
- 34
0
votes
1
answer
1k
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 ...
user881698
1
vote
0
answers
225
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,...
- 111
1
vote
1
answer
483
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:...
- 141
1
vote
0
answers
504
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 ...
- 3,140
2
votes
0
answers
2k
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:
- - - - - - - - - - - - - - - - - - - - - -...
- 117
3
votes
0
answers
1k
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....
- 646
0
votes
0
answers
638
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!
1
vote
2
answers
95
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 ...
- 555
1
vote
0
answers
1k
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 ...
- 21
1
vote
0
answers
1k
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/...
- 111
0
votes
0
answers
348
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:...
0
votes
2
answers
1k
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 ...
- 669
1
vote
2
answers
486
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 ...
0
votes
1
answer
4k
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
- 613
2
votes
2
answers
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 ...
- 91
2
votes
1
answer
2k
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/...
- 23
0
votes
2
answers
7k
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 ...
- 131
0
votes
0
answers
53
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 ...
- 61
1
vote
1
answer
2k
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 ...
- 163