Getting response of http request without content-length?
In HTTP/1.0 – server response without content-length is when the stream closes In HTTP/1.1 – server response without content-length is when the response is chunked encoded
tcp
Converting serial port data to TCP/IP in a Linux environment
You don’t need to write a program to do this in Linux. Just pipe the serial port through netcat: netcat www.example.com port </dev/ttyS0 >/dev/ttyS0 Just replace the address and port information. Also, you may be using a different serial port (i.e. change the /dev/ttyS0 part). You can use the stty or setserial commands to change … Read more
TCP sequence number question
The sequence number loops back to 0. Source: TCP sequence numbers and receive windows behave very much like a clock. The receive window shifts each time the receiver receives and acknowledges a new segment of data. Once it runs out of sequence numbers, the sequence number loops back to 0. Also see chapter 4 of … Read more
Relation between HTTP Keep Alive duration and TCP timeout duration
An open TCP socket does not require any communication whatsoever between the two parties (let’s call them Alice and Bob) unless actual data is being sent. If Alice has received acknowledgments for all the data she’s sent to Bob, there’s no way she can distinguish among the following cases: Bob has been unplugged, or is … Read more
Unwanted RST TCP packet with Scapy
The article you cited makes this pretty clear… Since you are not completing the full TCP handshake your operating system might try to take control and can start sending RST (reset) packets, to avoid this we can use iptables: iptables -A OUTPUT -p tcp –tcp-flags RST RST -s 192.168.1.20 -j DROP Essentially, the problem is … Read more
Why tcp termination need 4-way-handshake?
After googling a lot, I recognized that the four-way is actually two pairs of two-way handshakes. If termination is a REAL four-way actions, the 2 and 3 indeed can be set 1 at the same packet. But this a two-phase work: the first phase (i.e. the first two-way handshake) is : Client ——FIN—–> Server Client … Read more
TCP – difference between Congestion window and Receive window
To give a short answer: the receive window is managed by the receiver, who sends out window sizes to the sender. The window sizes announce the number of bytes still free in the receiver buffer, i.e. the number of bytes the sender can still send without needing an acknowledgement from the receiver. The congestion window … Read more
Does Alpine have known DNS issue within Kubernetes?
Yes, the Alpine images are known to be problematic in Kubernetes cluster concerning DNS queries. Even if it is not clear if the bug has been effectively fixed in any current version of Alpine, here are some related links: https://github.com/kubernetes-sigs/kind/issues/442 https://gitlab.alpinelinux.org/alpine/aports/-/issues/9017 https://github.com/gliderlabs/docker-alpine/issues/476 I encountered this problem on my side in my Kubernetes clusters as of … Read more
Cannot assign requested address – possible causes?
It turns out that the problem really was that the address was busy – the busyness was caused by some other problems in how we are handling network communications. Your inputs have helped me figure this out. Thank you. EDIT: to be specific, the problems in handling our network communications were that these status updates … Read more
EventMachine: “`start_tcp_server’: no acceptor (port is in use or requires root privileges)”
Had the same problem. Ran lsof -i :3000 (3000 is the port I ran it on). I found out that the port was being used by ruby. I killed the process using kill -9 *pid*. When I ran lsof -i :3000 again, nothing showed up. I then ran rails s and everything works fine now.