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Yesterday, I came across puzzling behavior in my home network. I was trying from host 192.168.1.A (macOS) to connect to a selenium cluster running on port 4444 on host 192.168.1.B (ubuntu), and kept ...
microtherion's user avatar
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I have a problem with reaching linux hosts through my home network, and I'd be glad for someone to point me in the right direction. I have a main wifi and wired router running DHCP. All IP addresses ...
cseprog's user avatar
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So, I want to use an SSH tunnel proxy occasionally. But I don't want to fire it up manually every time. And this is a laptop so if I just start the SSH tunnel at startup it might die of an occasional ...
Mikhail Ramendik's user avatar
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Digging into tcpdump implementation, I can see that it actually loads the libpcap.so dynamic library in userspace. However, by use of strace, I can't see any occurrence of calls to any function ...
CarloC's user avatar
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I made some network application. It is a client-server solution using the TCP/IP protocol. Clients connect to the server. They make several connections every second. Communication consists of units of ...
DaBler's user avatar
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I'm reading the Linux kernel implementation of the TCP/IP stack. Everything was ok till I encounter this figure while reading TCP/IP architecture, design and implementation in Linux As you may see ...
ca-hercor's user avatar
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I have a virtual machine (Linux) installed in my PC (Windows) and I was wondering the reachability of the IP address assigned to the virtual machine. According to ipconfig on Windows and ifconfig on ...
Yiyang Yan's user avatar
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My ISP/AS/NAT is problematic since I think it blocks some transfer-layer protocols. I want to check whether my connection to my domain behind a CDN (e.g. cloudflare) supports HTTP/2, gRPC, QUIC or ...
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I created a tcp server listening at [IP1:PORT1] and connect to it via a client using [IP2]. On both the client and server, SO_KEEPALIVE and TCP_USER_TIMEOUT are enabled with below config values. ...
Vishal Sharma's user avatar
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Here is how to reproduce this problem: Start a listen service on port 80: nc -l 80 -k Access this service using curl: curl 127.0.0.1 --interface eth0 Capture the packet using tcpdump both on eth0 and ...
Jack Yang's user avatar
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The highest TCP port number is 65535. If a router doing NAT uses an ephemeral port for each connection made to the internet on behalf of the hosts on the internal network, does this mean that it is ...
Flux's user avatar
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tshark get data from interface or pcap files. When it read data from interface, user has to write filter with -f (accortding to pcap-filter(7)) and when read from file user has to write filter with -Y ...
PersianGulf's user avatar
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Our company has 2 proxy servers that are running a vendor proprietary OS that is built on top of FreeBSD 11.2, we are having incidents on our business peak hours where proxy server stops accepting new ...
Zarkos.Fina's user avatar
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for studying purposes about TCP/IP, we should run a DNS server, i did the advised configuration, the server is runing without any erros, but when i request the server for the configured domain name ...
adil's user avatar
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I'm just confused with ping. As per my understanding, when I ping some IP address, it sends an ICMP message to the destination, and if there is no response, it get either "request timeout" ...
Vespene Gas's user avatar
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I'm trying to connect a TCP/IP device over ethernet adapter via ethernet cable. The connection is being seen in Network Manager and I can get output of ping command at least and I can't access a built-...
Dr. Herman Diracov's user avatar
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I have a number of servers to SSH into, and some of them, being behind different NATs, may require an SSH tunnel. Right now I'm using a single VPS for that purpose. When that number reaches 65535 - ...
ᴍᴇʜᴏᴠ's user avatar
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I am wondering what is tbe route for a packet sent from src being the docker container with its own 'dockerised' IP, to the IP address of the VM, on which this docker process runs? Will the packets ...
Bober02's user avatar
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I have two services listening on TCP/IPv6 sockets, ssh and mysql. ss shows this: $ ss -tl6 State Recv-Q Send-Q Local Address:Port Peer Address:Port LISTEN 0 128 ...
spinkus's user avatar
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I'm currently diagnosing a issue related to packet forwarding. I forward link layer packets to B network namespace and I found that B network namespace didn't reply to them, but I could curl and view ...
sqlbie's user avatar
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I'm in process building my own firewall. One can say I'm building user space TCP/IP stack. However, When Kernel receive packet that it can't identify, Kernel would send out RST + ACK (Not sure whether ...
sqlbie's user avatar
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I have a ubuntu machine with two interfaces (eth0 and eth1). Eth0 interface has a dhcp address and eth1 has apipa (169.254.x.x) address. eth1 is not connected and eth0 is connected to a local network. ...
Kumar's user avatar
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On a typical linux machine, how many times would packets be copied from the application layer to all the way in its journey to the network card. I am assuming the protocol being used here is TCP/IP ...
Shivam Jindal's user avatar
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I am a networking newb - ping cannot locate certain dns names, so I put them in /etc/hosts like this: 10.128.0.22 kafka.marathn.meso 10.128.0.31 elasticsearch.marathn.meso and then ping can find them....
Alexander Mills's user avatar
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telnet 8.8.8.8 8888 displays Trying... I was expecting, that this directly is refused. Background: When we have a NGINX reverse proxy server, it would be great, that it detects directly when the ...
Alex's user avatar
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I have a problem with a (remote) server running SCO UNIX. It's been working for years, but was recently moved, and I changed its IP address & gateway address. Since then it works perfectly until ...
Stan C's user avatar
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I'm using a PPP to communicate with a device. So far what I have been doing is instantiating PPP on my machine (Fedora 29) and on the device (Yocto Linux). Then I open a TCP/UDP socket and communicate ...
flashburn's user avatar
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I want to design a system which reduce travel time of packet what is happening in reality is I send a SYN bit from client side, this bit travel through router then to server and server reply SYN+ACK ...
ASid13's user avatar
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We are trying to setup a test bed for our server testing, to simulate multiple connection / msg handling, I am trying to connect to our test server from a virtual IP. on the client machine (Debian) ...
Ragav's user avatar
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So I have an IP Address 5x.2x.2xx.1xx I want to map to localhost. In my hosts file I have: cat /etc/hosts 127.0.1.1 test test 127.0.0.1 localhost # The following lines are desirable for IPv6 capable ...
user1532587's user avatar
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I'm playing around with tuning various tcp settings for high number of outgoing client connections. I've put following in my /etc/sysctl.conf on Ubuntu 16.04. net.ipv4.ip_local_port_range = 18000 ...
user avatar
6 votes
1 answer
5k views

I'm trying to connect directly (without 3rd party server) my computer to a friend's computer. We are both behind a ISP router, and would like (as a challenge!) to connect without modifying the router ...
Basj's user avatar
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Our nginx reported a error below: 2017/10/19 10:47:40 [crit] 41689#0: *23414459 connect() to 127.0.0.1:1234 failed (99: Cannot assign requested address) while connecting to upstream, client: 10.0.0.1,...
ponypaver's user avatar
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is there any body knows ; how a server answers to client what if they send first packet as non-syn or the server finish the connection and wait for a new connection instead of getting an ACK or push ...
FireBall's user avatar
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1 answer
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Doesn't port 80/http need to be explicitly opened like other ports (such as 443/https or 8080/server), or is it a special case? on my machine (CentOS Linux release 7.3.1611) firewall-cmd --list-...
theRiley's user avatar
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enabling syncookies is helping against some attacks but the official docs still say syncookies seriously violate TCP protocol, do not allow to use TCP extensions Today I discover that once upon ...
Massimo's user avatar
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219 views

I have the Beaglebone powered through 5V and the ethernet in a open port on my PC. I have added the lines to /etc/network/interfaces auto eth0 iface eth0 inet static address 192.168.1.80 ...
Caleb Hayward's user avatar
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Is there a means (kernel mode API) under Linux (any distro) that can identify the application path of a process that makes a connect() call and is attempting to access the internet ? Vice versa in the ...
David J's user avatar
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3 votes
0 answers
185 views

I have this situation: a piece of software got hardcoded IP address (let assume it is being 196.10.10.100:20000) to which it binds a socket and sends TCP and UDP traffic to 196.10.10.9:20000 (...
Swift's user avatar
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1 answer
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I'm generating traffic on a Linux host with pktgen. I thought I could intercept it with tc and apply certain actions, but apparently pktgen bypasses it and writes directly in driver. Is there a way to ...
Mark's user avatar
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5 votes
2 answers
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I have a server running on my Linux box, also on which the following commands were run: $ cat /proc/sys/net/ipv4/tcp_keepalive_time 7200 $ cat /proc/sys/net/ipv4/tcp_keepalive_intvl 75 $ cat /proc/sys/...
Wad's user avatar
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4 votes
1 answer
3k views

I am setting up an Arch/Manjaro-based machine that only occasionally will be connected to network. I.e. most of the time its Ethernet card is disconnected. I run into this curious problem - when I ...
r0berts's user avatar
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52 votes
4 answers
156k views

For testing purposes I need to create a shell script that connects with a remote IP>Port and sends a simple text TCPIP Socket message.
Bachalo's user avatar
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Linux kernel defines a timeout to destroy TIME-WAIT state of a connection in include/net/tcp.h: #define TCP_TIMEWAIT_LEN (60*HZ) Is there a way to change this parameter at runtime, via sysctl or /...
Mark's user avatar
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I have a client socket program and server socket program in C TCP/IP . I execute the server program first on a port say 5000 and then executes client program on the same port and then server respond ...
SecureTech's user avatar
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2 votes
1 answer
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I have two Ethernet-wired connected devices. I gave to both of them address from same sub-network. As result I can see second device in arp-table of the first. $ arp -a ? (128.247.77.90) at 10:60:4b:...
Dropper's user avatar
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5 votes
1 answer
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How do I configure Docker containers to have unique IP addresses that are not the default ones? The Docker containers will run Apache or some web service. These Docker containers will share one host ...
Kiran's user avatar
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I have an Ubuntu 14.04 LTS, kernel 3.13 in a Intel Xeon + 8Gb box. It has apache 2.4.7 configured in mpm worker with up to 4000 workers. The max bandwidth allowed by the ISP is 100Mbps. If I test ...
David's user avatar
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7 votes
3 answers
62k views

I am testing my Debian Server with some Nmap port Scanning. My Debian is a Virtual Machine running on a bridged connection. Classic port scanning using TCP SYN request works fine and detects port 80 ...
hg8's user avatar
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I have connected a computer (running Debian Wheezy) to two different DHCP servers (routers) through a cable and through a wifi device. If I look at the routes with route, I get the following result ...
Giorgio's user avatar
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