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Questions tagged [tcp]

The Transmission Control Protocol (TCP) is a core protocol of the Internet protocol suite.

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Is there way to disable tcp timestamps in macOS?

I am using macOS Ventura 13.3. I know that in Windows and Linux I can enable/disable TCP timestamps via netsh and sysctl commands. In Linux, it is the net.ipv4.tcp_timestamps parameter. macOS has the ...
Art Spasky's user avatar
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How to properly trigger path mtu discovery

I've activate the pmtu attribute in my machine. sysctl net.inet.tcp.path_mtu_discovery net.inet.tcp.path_mtu_discovery: 1 then I've used /usr/bin/nscurl to send messages to a remote gateway with mtu=...
Zohar81's user avatar
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weird connection request on macos m1 nettop

I see a weird connection request on macos m1 for nettop. This happens on other programs as well. these ips are blocked, but I am wondering what is causing this. This happens specifically on macos, ...
CarriMegrabyan's user avatar
-1 votes
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Macbook Pro - How do we terminate ALL ESTABLISHED connections?

How do I terminate ALL the ESTABLISHED tcp connections in Terminal? I can use the command below to get a list of active & established connections: netstat -anvp tcp | awk 'NR<3 || /ESTABLISHED/‘...
Santhosh's user avatar
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Detect which process is attempting TCP connections

On my MacBook Pro (Monterey), I was looking at packet captures over a period of a few hours and I noticed that something on my box is, every few minutes, pinging other computers on the local network ...
Daniel Walker's user avatar
2 votes
1 answer
2k views

Strange Ports opened on my Iphone?

I've run NMAP several times on my home network in my campaign of learning the basics of network security. So far all my devices except my PC have been Iphones/Chromebooks so nothing has been found in ...
N S's user avatar
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2 answers
308 views

What is the Bonjour service _acp-sync._tcp used for? And why is it accessing my Apple AirPort Base station using a long and obscure string?

Scanning for Bonjour devices on my network shows a long and obscure string associated with my AirPort Base station using this Bonjour protocol _acp-sync._tcp. What is this? What is it for?
Timothy Childers's user avatar
1 vote
1 answer
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Reset TCP/IP Stack without Rebooting?

This is a bit of an unusual question but I have a Mac server that gets hit with a lot of DDoS attacks. Usually my data center's mitigation system catches them but sometimes they slip through. When ...
l008com's user avatar
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3 votes
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What is `intu-ec-client` listening on TCP port 8021?

I'm wondering how I can either kill it or change the port it listens on. Neither lsof -nP -i4TCP:8021 | grep LISTEN nor netstat -av | grep 8021 or launchctl list | awk 'NR>1 {print $3}' | xargs -I %...
n370's user avatar
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Blocking SYN-Flood Attacks?

I've got a Mac web server that's been getting hit pretty regularly with SYN half-open attacks. I've looked in to various ways to combat this. I've found a lot of general information, but not very much ...
l008com's user avatar
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Why my mac can not access external traffic to other port except 80, 443, 22?

I can access all website with standard port(80 and 443) example: domain.com, but why I cant access example.com:3030? I cant connect to MySQL and PostgreSQL, via direct host/port to external IP, but I ...
Muhammad Dyas Yaskur's user avatar
3 votes
2 answers
970 views

sysctl setting net.inet.tcp.keepidle removed in 10.15. Is there a replacement setting?

My work requires long-running connections to databases that required this sysctl setting in earlier OSX versions. Since it no longer exists, these connections appear to remain open, but they ...
Brian G's user avatar
  • 31
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2 answers
3k views

Can't connect to TCP/IP printer with undescore "_" in the IP

I have a wireless printer that's connected to our private LAN in our workplace. There is a weird configuration for the printer that it requires two printers to be added. For color - 192.168.51.xxx and ...
HenrijsS's user avatar
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9 votes
3 answers
12k views

Packet sniffer for MacOS Mojave and above

I'm looking for a packet sniffer app that runs on MacOS in a GUI (I know I can accomplish some functionality with native CLI utilities like tcpdump). Previously I used Packet Peeper, however it doesn'...
Orun's user avatar
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1 answer
274 views

Have DHCP for Wi-Fi and static IP for Ethernet?

I'm trying to connect to a device over Ethernet and set a static IP for the Ethernet to talk to the device. When I do this, I can talk to the device but it kills connection to the Wi-Fi and I can't ...
John Doenut's user avatar
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Why is IMRemoteURLConnectionAgent contacting a Charter IP address

I never use iMessage. I never use iCloud. And yet I happened to check my Mac's current network connections and I found this: IMRemoteURLConn 33557 me 7u IPv4 ... 0t0 TCP 192.168.1.198:57996-&...
Dingo's user avatar
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1 answer
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Login to AppStore over cellular data, jump on public wifi, download/install app is "safe"?

Is it "safe" to install an App as such: (1) using only a cellular data connection (wifi turned off) login to the App Store. (2) enable wifi. (3) connect to public wifi network. (4) disable cellular ...
Just Someone's user avatar
2 votes
1 answer
823 views

How does WireShark work on OS X? What processes does it interact with?

I'm looking for deep/detailed research into how the MacOS TCP stack works. Namely, what are the files/Dynamic Libraries that offer this service? What Libraries does WireShark interact with? My goal ...
makerofthings7's user avatar
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1 answer
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How to force open TCP 443 on my machine?

I turned off the firewall. Then, using nmap in the terminal, I issued the statement nmap 127.0.0.1 and got Starting Nmap 7.12 ( https://nmap.org ) at 2016-08-15 11:00 PHT Nmap scan report for ...
Abel Melquiades Callejo's user avatar
2 votes
2 answers
3k views

How to inspect TCP/IP packets

How can I inspect IP packets send through currently open TCP connections? I opened a nettop utility in Terminal, which I think lists IP packet, but doesn't tell anything about their content, namely ...
sanjihan's user avatar
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4 votes
1 answer
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Which process is using port 4000 (identified as remoteanything by nmap)?

I've run nmap -sS [computer ip] and see that i only have one service running: PORT STATE SERVICE 4000/tcp open remoteanything What service is this? Should i close it? I've googled and only ...
rostgaard's user avatar
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How to increase value of tcbhashsize parameter in OS X

I am running OS X 10.11 - El Capitan. I am trying to tune my TCP setting for better network / Internet performance. Most of the settings I have been able to modify permanently through /etc/sysctl.conf ...
Anthony's user avatar
  • 101
6 votes
1 answer
4k views

How to Use Terminal for "Little Snitch" Functionality without Little Snitch

I'm a Terminal newb, and trying to wrap my head around manual "Little Snitch" functionality without using Little Snitch. From the research I've been doing, I've landed on the fact that I need to ...
bmoneruxui's user avatar
1 vote
2 answers
1k views

How to put Wifi card in monitor mode?

When I run tcpdump, I do so after having connected to an access point. Is there a way to run tcpdump without having connected already?
hap's user avatar
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1 answer
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How to enable echo service for tcp or udp on well-known port 7 on Mac OS X 10.8 or above?

I am learning TCP/IP protocol with a Mac, and need echo service (refer to [RFC 862], or Wiki) to test network. But it seems to OS X doesn't implement it or disable it. I learned that launchd replaced ...
aruku7230's user avatar
  • 103
9 votes
2 answers
36k views

OS X - List all active sockets

I'm looking for a simple command that will list ALL currently active and/or otherwise bound TCP & UDP sockets, corresponding port numbers and their respective states (i.e. ESTABLISHED, LISTEN, ...
voices's user avatar
  • 2,229
2 votes
1 answer
665 views

Find who is intercepting traffic on port 80

Every 7–10 days, all internet browsing on my Mac stops working. I can use Firefox, Safari, Chrome, but I'm able to surf only Google and few other sites. So I tried to telnet a webserver on the local ...
giox069's user avatar
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3 votes
1 answer
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How can I limit bandwidth for a specific port/app in OS X 10.10 Yosemite?

I am running OS X 10.10 Yosemite, and I am looking for a way to limit upload bandwidth specifically on TCP port 8333, so I can run Bitcoin Core to contribute outgoing bandwidth without completely ...
Maximillian Laumeister's user avatar
2 votes
0 answers
111 views

Limiting TCP connections

How can I limit TCP connections on Mac using Terminal? I used iptables on Linux (eOS) to limit the connections of an application (Ace Stream Player) as follows: $iptables -A OUTPUT -m limit --limit ...
Andy's user avatar
  • 125
0 votes
1 answer
5k views

Network Ports Used To Print (Network LPD Printing)

I have been experimenting with an application that listens to network ports below 1024. I discovered that when that application is running, an attempt to print to a network printer (set up to print ...
Bart Silverstrim's user avatar
2 votes
1 answer
3k views

How to increase max socket connections for Yosemite 10.10

I'm trying to test a network service app that allows for a large number of simultaneous socket connections. I have adjusted /etc/sysctl.conf with the following: kern.maxfiles=65536 kern....
Caffeine Coma's user avatar
6 votes
2 answers
34k views

How to interface with iOS lockdownd

I used nmap to portscan my iPod Touch, and found a single port open, which was port 62078, labeled as "iphone-sync". I did some research, and found that the proccess behind it was a program called "...
Dessa Simpson's user avatar
3 votes
3 answers
1k views

I have a service listening on a port, how do I open the port externally?

I have a service that is listening on a tcp port, and it is listed with this command: >netstat -atp tcp | grep -i "listen" tcp4 0 0 192.168.2.5.8070 *.* LISTEN ...
Jonas's user avatar
  • 6,372
2 votes
1 answer
2k views

TCP Congestion Control Algorithm of OSX10.7

How can I find out which algorithm OSX10.7 uses (NewReno, SACK, Tahoe...) and if possible, how can I change it?
user63836's user avatar
6 votes
4 answers
2k views

Open ports. Safe?

My friend is currently running the default firewall with "Block all incoming connection" (except the basic ones like 80). I just scanned his mac for open ports and I found the following: Open TCP ...
DevRandom's user avatar
  • 163
0 votes
1 answer
95 views

save IPv4 address for different WIFI

I have a macbook pro, that I use at work and in my house, the problem is that i have to set up manually the TCP/IP IPv4 address for each place, the address doesn't change once im on a location, but I ...
manuelBetancurt's user avatar
2 votes
1 answer
737 views

How do I further diagnose TCP connectivity (timeout) problems? (ICMP, DNS work fine)

I have two Macs behind a cable modem/WAP. One works fine. The other is able to ping servers but is unable to telnet to them. For instance pinging what.org works fine but I get operation timed out ...
user40344's user avatar
1 vote
1 answer
3k views

How can I ping a given host behind an Airport Extreme Base Station

I have an Airport Extreme Base Station (7.6.1) which has a public ip address on the WAN side. I have many hosts on the LAN side. I would like to configure the AEBS such that pings sent from the ...
Scott's user avatar
  • 895
3 votes
1 answer
5k views

Postfix SMTP server slow to accept incoming connection

I have a snow-leopard os-x Server configuration running postfix with no local firewall on the X-Serve. When a client attempts to connect to the SMTP port the connection takes about 15 seconds to ...
sweetfa's user avatar
  • 317
2 votes
1 answer
434 views

How do I turn the echo service on in Snow Leopard?

I'd like to temporarily turn on the echo service (TCP and UDP port 7) on in Mac OS 10.6 (Snow Leopard). I guess this involves using the launchctl/launchd?
trojanfoe's user avatar
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7 votes
1 answer
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How do you set the TCP congestion control algorithm on OS X?

I would like to set the TCP congestion control algorithm to Westwood+. Is this possible in OS X?
Shawn J. Goff's user avatar