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| <h3 class="section">16.2 Communication Styles</h3> |
| |
| <p>The GNU library includes support for several different kinds of sockets, |
| each with different characteristics. This section describes the |
| supported socket types. The symbolic constants listed here are |
| defined in <samp><span class="file">sys/socket.h</span></samp>. |
| <a name="index-sys_002fsocket_002eh-1647"></a> |
| <!-- sys/socket.h --> |
| <!-- BSD --> |
| |
| <div class="defun"> |
| — Macro: int <b>SOCK_STREAM</b><var><a name="index-SOCK_005fSTREAM-1648"></a></var><br> |
| <blockquote><p>The <code>SOCK_STREAM</code> style is like a pipe (see <a href="Pipes-and-FIFOs.html#Pipes-and-FIFOs">Pipes and FIFOs</a>). |
| It operates over a connection with a particular remote socket and |
| transmits data reliably as a stream of bytes. |
| |
| <p>Use of this style is covered in detail in <a href="Connections.html#Connections">Connections</a>. |
| </p></blockquote></div> |
| |
| <!-- sys/socket.h --> |
| <!-- BSD --> |
| <div class="defun"> |
| — Macro: int <b>SOCK_DGRAM</b><var><a name="index-SOCK_005fDGRAM-1649"></a></var><br> |
| <blockquote><p>The <code>SOCK_DGRAM</code> style is used for sending |
| individually-addressed packets unreliably. |
| It is the diametrical opposite of <code>SOCK_STREAM</code>. |
| |
| <p>Each time you write data to a socket of this kind, that data becomes |
| one packet. Since <code>SOCK_DGRAM</code> sockets do not have connections, |
| you must specify the recipient address with each packet. |
| |
| <p>The only guarantee that the system makes about your requests to |
| transmit data is that it will try its best to deliver each packet you |
| send. It may succeed with the sixth packet after failing with the |
| fourth and fifth packets; the seventh packet may arrive before the |
| sixth, and may arrive a second time after the sixth. |
| |
| <p>The typical use for <code>SOCK_DGRAM</code> is in situations where it is |
| acceptable to simply re-send a packet if no response is seen in a |
| reasonable amount of time. |
| |
| <p>See <a href="Datagrams.html#Datagrams">Datagrams</a>, for detailed information about how to use datagram |
| sockets. |
| </p></blockquote></div> |
| |
| <!-- sys/socket.h --> |
| <!-- BSD --> |
| <div class="defun"> |
| — Macro: int <b>SOCK_RAW</b><var><a name="index-SOCK_005fRAW-1650"></a></var><br> |
| <blockquote><p>This style provides access to low-level network protocols and |
| interfaces. Ordinary user programs usually have no need to use this |
| style. |
| </p></blockquote></div> |
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