SOCKET(3POSIX)

💖 SOCKET(3POSIX) — the POSIX Programmer's Manual, but make it cute 💖

okay bestie, gather round because we're about to talk about the absolute main character of networking: socket(). This page lives in the POSIX Programmer's Manual (yes, that one), and it's the blueprint for creating an endpoint for communication. iconic behavior honestly ✨

⚠️ PROLOG tea first, bestie: this manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (so go consult the corresponding Linux manual page for the deets on Linux behavior), or the interface may not be implemented on Linux at all. 💀 Don't come for me, I'm just the messenger.

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✨ NAME ✨

socket — create an endpoint for communication 🦋

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🌸 SYNOPSIS 🌸

#include <sys/socket.h>

int socket(int domain, int type, int protocol);

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💅 DESCRIPTION 💅

Okay so here's the vibe. The socket() function shall create an unbound socket in a communications domain, and return a file descriptor that can be used in later function calls that operate on sockets. That file descriptor shall be allocated as described in Section 2.14, File Descriptor Allocation. Periodt. 🎀

The socket() function takes the following arguments:

• domain — Specifies the communications domain in which a socket is to be created. 🗺️
• type — Specifies the type of socket to be created. 🧚
• protocol — Specifies a particular protocol to be used with the socket. Specifying a protocol of 0 causes socket() to use an unspecified default protocol appropriate for the requested socket type. (aka "you pick, bestie") 🙈

The domain argument specifies the address family used in the communications domain. The address families supported by the system are implementation-defined — so like, read your system's manual, not mine. 😭

Symbolic constants that can be used for the domain argument are defined in the <sys/socket.h> header. 📚

The type argument specifies the socket type, which determines the semantics of communication over the socket. The following socket types are defined; implementations may specify additional socket types:

• SOCK_STREAM — Provides sequenced, reliable, bidirectional, connection-mode byte streams, and may provide a transmission mechanism for out-of-band data. The dependable one. The ride-or-die. 💖
• SOCK_DGRAM — Provides datagrams, which are connectionless-mode, unreliable messages of fixed maximum length. She's fast and she's free and she might ghost you. 💀
• SOCK_SEQPACKET — Provides sequenced, reliable, bidirectional, connection-mode transmission paths for records. A record can be sent using one or more output operations and received using one or more input operations, but a single operation never transfers part of more than one record. Record boundaries are visible to the receiver via the MSG_EOR flag. Structured queen behavior. 👑

If the protocol argument is non-zero, it shall specify a protocol that is supported by the address family. If the protocol argument is zero, the default protocol for this address family and type shall be used. The protocols supported by the system are implementation-defined. 🌀

The process may need to have appropriate privileges to use the socket() function or to create some sockets. So if it's giving permission-denied energy, that might be why. 🔐

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🔥 RETURN VALUE 🔥

Upon successful completion, socket() shall return a non-negative integer — the socket file descriptor. Slay. ✨

Otherwise, a value of -1 shall be returned and errno set to indicate the error. Not slay. 😭

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🎀 ERRORS 🎀

The socket() function shall fail if:

• EAFNOSUPPORT — The implementation does not support the specified address family.
• EMFILE — All file descriptors available to the process are currently open.
• ENFILE — No more file descriptors are available for the system.
• EPROTONOSUPPORT — The protocol is not supported by the address family, or the protocol is not supported by the implementation.
• EPROTOTYPE — The socket type is not supported by the protocol.

The socket() function may fail if:

• EACCES — The process does not have appropriate privileges.
• ENOBUFS — Insufficient resources were available in the system to perform the operation.
• ENOMEM — Insufficient memory was available to fulfill the request.

The following sections are informative. (aka, the gossip sections, not the law 📖)

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🌈 EXAMPLES 🌈

None. Literally none. The void. Empty. 🫥

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🦋 APPLICATION USAGE 🦋

The documentation for specific address families specifies which protocols each address family supports. The documentation for specific protocols specifies which socket types each protocol supports. So like, cross-reference, bestie, it's giving research paper. 🔍

The application can determine whether an address family is supported by trying to create a socket with domain set to the protocol in question. Very "just ask and see what happens" of you. 💅

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⭐ RATIONALE ⭐

None. (She said no thoughts, head empty. 🧠✨)

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🌟 FUTURE DIRECTIONS 🌟

None. (The future is bright and also unspecified. 😌)

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💜 SEE ALSO 💜

• Section 2.14, File Descriptor Allocation
• accept()
• bind()
• connect()
• getsockname()
• getsockopt()
• listen()
• recv()
• recvfrom()
• recvmsg()
• send()
• sendmsg()
• setsockopt()
• shutdown()
• socketpair()

The Base Definitions volume of POSIX.1‐2017, <netinet_in.h>, <sys_socket.h>

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👑 COPYRIGHT 👑

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .

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and that's the whole page, bestie 🫶 this little love letter was brought to you by IEEE/The Open Group, stamped 2017, and it's the SOCKET(3POSIX) page itself. go forth and socket() responsibly 💖✨