S Guide to Network Programming. S Guide to Network Programming. Using Internet Sockets Brian "Beej Jorgensen" Hall firstname.lastname@example.org Version 3.0.15 July 3, 2012.
Handle multiple socket connections with fd_set and select on Linux. #include <stdio.h> #include <string.h> //strlen #include <stdlib.h> #include <errno.h> #include <unistd.h> //close #include <arpa/inet.h> //close #include <sys/types.h>
The World of select() So just why am I so hyped on select()?
One traditional way to write network servers is to have the main server block on accept(), waiting for a connection. Once a connection comes in, the server fork()s, the child process handles the connection and the main server is able to service new incoming requests. Introduction to non-blocking I/O. Programs that use non-blocking I/O tend to follow the rule that every function has to return immediately, i.e. all the functions in such programs are nonblocking.
Thus control passes very quickly from one routine to the next. You have to understand the overall picture to some extent before any one piece makes sense. (This makes it harder to get your mind around than the same program written with blocking calls, but the benefits mentioned elsewhere in this document make up for this trouble, so don't be discouraged.)
Many objects need to wait for time to pass or for an external event to occur, but because their methods must return immediately, they can't do the obvious or natural thing. Instead, they use the "state machine" technique. IEEE 802.11. IEEE 802.11 is a set of media access control (MAC) and physical layer (PHY) specifications for implementing wireless local area network (WLAN) computer communication in the 2.4, 3.6, 5 and 60 GHz frequency bands.
They are created and maintained by the IEEE LAN/MAN Standards Committee (IEEE 802). The base version of the standard was released in 1997 and has had subsequent amendments. The standard and amendments provide the basis for wireless network products using the Wi-Fi brand. While each amendment is officially revoked when it is incorporated in the latest version of the standard, the corporate world tends to market to the revisions because they concisely denote capabilities of their products. As a result, in the market place, each revision tends to become its own standard. DHCP. Time to live. IP packets DNS records TTLs also occur in the Domain Name System (DNS), where they are set by an authoritative name server for a particular resource record.
When a caching (recursive) nameserver queries the authoritative nameserver for a resource record, it will cache that record for the time (in seconds) specified by the TTL. If a stub resolver queries the caching nameserver for the same record before the TTL has expired, the caching server will simply reply with the already cached resource record rather than retrieve it from the authoritative nameserver again. Network interface controller. "Network card" redirects here.
For the British Rail discount card, see Network Railcard. A network interface controller (NIC, also known as a network interface card, network adapter, LAN adapter, Physical Network Interface and by similar terms) is a computer hardware component that connects a computer to a computer network. Early network interface controllers were commonly implemented on expansion cards that plugged into a computer bus. The low cost and ubiquity of the Ethernet standard means that most newer computers have a network interface built into the motherboard. Purpose The network controller implements the electronic circuitry required to communicate using a specific physical layer and data link layer standard such as Ethernet, Fibre Channel, Wi-Fi or Token Ring. Although other network technologies exist, IEEE 802 networks including the Ethernet variants have achieved near-ubiquity since the mid-1990s.
NAT. NAT. IPv6. IPv6 (англ.
Internet Protocol version 6) — новая версия протокола IP, призванная решить проблемы, с которыми столкнулась предыдущая версия (IPv4) при её использовании в интернете, за счёт использования длины адреса 128 бит вместо 32. Протокол был разработан IETF. В настоящее время протокол IPv6 уже используется в нескольких тысячах сетей по всему миру (более 14000 сетей на осень 2013), но пока ещё не получил столь широкого распространения в Интернете, как IPv4.
На конец 2012 года, доля IPv6 сетевого трафика составляла около 1%. К концу 2013 года ожидается рост до 3%. После того, как адресное пространство в IPv4 закончится, два стека протоколов — IPv6 и IPv4 — будут использоваться параллельно (англ. dual stack), с постепенным увеличением доли трафика IPv6 по сравнению с IPv4. IPv4. Internet Protocol version 4 (IPv4) is the fourth version in the development of the Internet Protocol (IP) Internet, and routes most traffic on the Internet. However, a successor protocol, IPv6, has been defined and is in various stages of production deployment.
IPv4 is described in IETF publication RFC 791 (September 1981), replacing an earlier definition (RFC 760, January 1980). IPv4 is a connectionless protocol for use on packet-switched networks. It operates on a best effort delivery model, in that it does not guarantee delivery, nor does it assure proper sequencing or avoidance of duplicate delivery. These aspects, including data integrity, are addressed by an upper layer transport protocol, such as the Transmission Control Protocol (TCP). Port (computer networking) In computer networking, a port is a software construct serving as a communications endpoint in a computer's host operating system.
A port is always associated with an IP address of a host and the protocol type of the communication. It completes the destination or origination address of a communications session. A port is identified for each address and protocol by a 16-bit number, commonly known as the port number. Specific, well-known port numbers are often used to identify specific applications and services. Of the thousands of enumerated ports, 1024 well-known port numbers are reserved by convention to identify specific service types on a host. In the client-server model of application architecture, ports are used to provide a multiplexing service on each port number that network clients connect to for service initiation, after which communication is reestablished on another connection-specific port number.
Port connection attempts are frequently monitored and logged by computers.