This function returns the number of bytes transmitted, or -1 on failure. In the Internet namespace, a socket address consists of a host address and a port on that host. Use unlink or remove to do this; see section Deleting Files. But, like pipes, sockets do not support file positioning operations. If your flags argument is zero, you can just as well use write instead of send ; see section Input and Output Primitives.

netdb h library

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netdb h library

Alternatively, you can test for pending out-of-band data, or wait until there is out-of-band data, using the select function; it can wait for an exceptional condition on the socket. The possible values of flags are described Libraty section Socket Data Options. This is so that the server can direct a message back to the client.

There is a database that keeps track of these, and you can use the getservbyname function to map a service name onto a port number; see section The Services Database. The first word in arguments is argument zero, which should by convention be the program name itself sans directories. In addition, the librsry you choose serves effectively as a part of the address because local port numbers are meaningful only within a particular protocol.

This is useful when the meaning of out-of-band data is “cancel everything sent so far”. This special constant saves you the trouble of looking up the address of your own machine.

The accept function waits if there are no connections pending, unless the socket socket has nonblocking mode set. You can also scan the whole protocols database one protocol at a time by using setprotoentgetprotoentand endprotoent.


The GNU C Library – Sockets

The argument how specifies what action to perform:. For reliable datagram communication, the default is RDP “reliable datagram protocol”. The size argument specifies the number of bytes to be transmitted.

netdb h library

The service field says which service this program provides. The file descriptor returned by the socket libgary supports both read and write operations. The value of the option is passed in the buffer optvalwhich has size optlen.

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When a socket finds that out-of-band data is on its way, it sends a SIGURG signal to the owner process or process group of the socket. For example, the protocol implements things like checksums to detect errors in transmissions, and routing instructions for messages. The return value and error conditions are also the same as for sendbut you cannot rely on the system to detect errors and report them; the most common error is that the packet is lost or there is no one at the specified address to receive it, and the operating system on your machine usually does not know this.

You can use select to wait for a pending connection, with a nonblocking socket.

The BSD UNIX Socket Library : Header Files

The peer process closed the socket lubrary your process was finished with it. When a socket has a default destination, then you can use send see section Sending Data or even write see section Input and Output Primitives to send a packet there. You can then call gethostent to read the entries. Ordinary read operations do not read out-of-band data; they read only the ordinary data.

The ljbrary value and error codes for setsockopt are the same as for getsockopt. You can specify a null pointer as the addr argument if you are not interested in this information. This function returns the number of bytes transmitted, or -1 on failure.


This makes for more efficiency if you call those functions several times, by avoiding reopening the database for each call. Librafy socket address in the Internet namespace consists of a machine’s Internet address plus a port number which distinguishes the sockets on a given machine for a given protocol.

This describes whether the option applies to the socket interface, or to a lower-level communications protocol interface. If the stayopen argument is nonzero, this sets a flag so that subsequent calls to getprotobyname or getprotobynumber will not close the librray as they usually would. Regardless of the namespace, you use the same functions bind and getsockname to set and examine a socket’s address.

Each time you write data to a socket of this kind, that data becomes one packet. When a server receives a connection request, it can complete the connection by accepting the request. The functions and symbols for dealing with socket addresses were named inconsistently, sometimes using the term “name” and sometimes using “address”.

You can call connect on a datagram socket, but this only specifies a default destination for further data transmission on the socket. Some computers put the most significant byte within a word first this is called “big-endian” orderand others put it last “little-endian” order.