418 lines
17 KiB
ReStructuredText
418 lines
17 KiB
ReStructuredText
==================
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Network Interfaces
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==================
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NuttX supports a BSD-compatible socket interface layer. These socket
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interface can be enabled by settings in the architecture `configuration
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file <NuttXConfigVariables.html>`__. Those socket APIs are discussed in
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the following paragraphs.
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- :c:func:`socket`
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- :c:func:`bind`
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- :c:func:`connect`
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- :c:func:`listen`
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- :c:func:`accept`
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- :c:func:`send`
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- :c:func:`sendto`
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- :c:func:`recv`
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- :c:func:`recvfrom`
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- :c:func:`setsockopt`
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- :c:func:`getsockopt`
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.. c:function:: int socket(int domain, int type, int protocol);
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Creates an endpoint for communication and
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returns a descriptor.
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:param domain: (see sys/socket.h)
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:param type: (see sys/socket.h)
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:param protocol: (see sys/socket.h)
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:return:
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0 on success; -1 on error with
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``errno`` set appropriately:
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- ``EACCES``. Permission to create a socket of the specified type
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and/or protocol is denied.
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- ``EAFNOSUPPORT``. The implementation does not support the specified
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address family.
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- ``EINVAL``. Unknown protocol, or protocol family not available.
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- ``EMFILE``. Process file table overflow.
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- ``ENFILE`` The system limit on the total number of open files has
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been reached.
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- ``ENOBUFS`` or ``ENOMEM``. Insufficient memory is available. The
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socket cannot be created until sufficient resources are freed.
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- ``EPROTONOSUPPORT``. The protocol type or the specified protocol is
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not supported within this domain.
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.. c:function:: int bind(int sockfd, const struct sockaddr *addr, socklen_t addrlen)
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Gives the socket sockfd the local address
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``addr``. ``addr`` is ``addrlen`` bytes long. Traditionally, this is
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called "assigning a name to a socket." When a socket is created with
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``socket()``, it exists in a name space (address family) but has no name
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assigned.
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:param sockfd: Socket descriptor from socket.
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:param addr: Socket local address.
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:param addrlen: Length of ``addr``.
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:return: 0 on success; -1 on error with ``errno`` set appropriately:
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- ``EACCES`` The address is protected, and the user is not the
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superuser.
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- ``EADDRINUSE`` The given address is already in use.
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- ``EBADF`` ``sockfd`` is not a valid descriptor.
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- ``EINVAL`` The socket is already bound to an address.
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- ``ENOTSOCK`` ``sockfd`` is a descriptor for a file, not a socket.
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.. c:function:: int connect(int sockfd, const struct sockaddr *addr, socklen_t addrlen);
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``connect()`` connects the socket referred to by the
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file descriptor ``sockfd`` to the address specified by ``addr``. The
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``addrlen`` argument specifies the size of ``addr``. The format of the
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address in ``addr`` is determined by the address space of the socket
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sockfd. If the socket sockfd is of type SOCK_DGRAM then ``addr`` is the
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address to which datagrams are sent by default, and the only address
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from which datagrams are received. If the socket is of type SOCK_STREAM
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or SOCK_SEQPACKET, this call attempts to make a connection to the socket
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that is bound to the address specified by ``addr``. Generally,
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connection-based protocol sockets may successfully ``connect()`` only
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once; connectionless protocol sockets may use ``connect()`` multiple
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times to change their association. Connectionless sockets may dissolve
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the association by connecting to an address with the sa_family member of
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sockaddr set to AF_UNSPEC.
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**Input Parameters:**
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- ``sockfd``: Socket descriptor returned by ``socket()``
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- ``addr``: Server address (form depends on type of socket)
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- ``addrlen``: Length of actual ``addr``
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**Returned Value:** 0 on success; -1 on error with
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```errno`` <#ErrnoAccess>`__ set appropriately:
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``EACCES`` or EPERM: The user tried to connect to a broadcast address
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without having the socket broadcast flag enabled or the connection
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request failed because of a local firewall rule.
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``EADDRINUSE`` Local address is already in use.
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``EAFNOSUPPORT`` The passed address didn't have the correct address
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family in its sa_family field.
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``EAGAIN`` No more free local ports or insufficient entries in the
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routing cache. For PF_INET.
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``EALREADY`` The socket is non-blocking and a previous connection
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attempt has not yet been completed.
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``EBADF`` The file descriptor is not a valid index in the descriptor
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table.
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``ECONNREFUSED`` No one listening on the remote address.
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``EFAULT`` The socket structure address is outside the user's address
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space.
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``EINPROGRESS`` The socket is non-blocking and the connection cannot be
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completed immediately.
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``EINTR`` The system call was interrupted by a signal that was caught.
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``EISCONN`` The socket is already connected.
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``ENETUNREACH`` Network is unreachable.
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``ENOTSOCK`` The file descriptor is not associated with a socket.
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``ETIMEDOUT`` Timeout while attempting connection. The server may be too
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busy to accept new connections.
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.. c:function:: int listen(int sockfd, int backlog);
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To accept connections, a socket is first created with
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``socket()``, a willingness to accept incoming connections and a queue
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limit for incoming connections are specified with ``listen()``, and then
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the connections are accepted with ``accept()``. The ``listen()`` call
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applies only to sockets of type ``SOCK_STREAM`` or ``SOCK_SEQPACKET``.
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**Input Parameters:**
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- ``sockfd``: Socket descriptor of the bound socket.
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- ``backlog``: The maximum length the queue of pending connections may
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grow. If a connection request arrives with the queue full, the client
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may receive an error with an indication of ECONNREFUSED or, if the
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underlying protocol supports retransmission, the request may be
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ignored so that retries succeed.
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**Returned Value:** On success, zero is returned. On error, -1 is
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returned, and ```errno`` <#ErrnoAccess>`__ is set appropriately.
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- ``EADDRINUSE``: Another socket is already listening on the same port.
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- ``EBADF``: The argument ``sockfd`` is not a valid descriptor.
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- ``ENOTSOCK``: The argument ``sockfd`` is not a socket.
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- ``EOPNOTSUPP``: The socket is not of a type that supports the listen
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operation.
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.. c:function:: int accept(int sockfd, struct sockaddr *addr, socklen_t *addrlen);
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The ``accept()`` function is used with connection-based
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socket types (``SOCK_STREAM``, ``SOCK_SEQPACKET`` and ``SOCK_RDM``). It
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extracts the first connection request on the queue of pending
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connections, creates a new connected socket with most of the same
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properties as ``sockfd``, and allocates a new socket descriptor for the
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socket, which is returned. The newly created socket is no longer in the
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listening state. The original socket ``sockfd`` is unaffected by this
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call. Per file descriptor flags are not inherited across an accept.
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The ``sockfd`` argument is a socket descriptor that has been created
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with ``socket()``, bound to a local address with ``bind()``, and is
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listening for connections after a call to ``listen()``.
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On return, the ``addr`` structure is filled in with the address of the
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connecting entity. The ``addrlen`` argument initially contains the size
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of the structure pointed to by ``addr``; on return it will contain the
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actual length of the address returned.
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If no pending connections are present on the queue, and the socket is
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not marked as non-blocking, accept blocks the caller until a connection
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is present. If the socket is marked non-blocking and no pending
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connections are present on the queue, accept returns ``EAGAIN``.
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**Input Parameters:**
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- ``sockfd``: Socket descriptor of the listening socket.
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- ``addr``: Receives the address of the connecting client.
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- ``addrlen``: Input: allocated size of ``addr``, Return: returned size
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of ``addr``.
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**Returned Value:** Returns -1 on error. If it succeeds, it returns a
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non-negative integer that is a descriptor for the accepted socket.
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- ``EAGAIN`` or ``EWOULDBLOCK``: The socket is marked non-blocking and
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no connections are present to be accepted.
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- ``EBADF``: The descriptor is invalid.
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- ``ENOTSOCK``: The descriptor references a file, not a socket.
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- ``EOPNOTSUPP``: The referenced socket is not of type ``SOCK_STREAM``.
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- ``EINTR``: The system call was interrupted by a signal that was
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caught before a valid connection arrived.
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- ``ECONNABORTED``: A connection has been aborted.
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- ``EINVAL``: Socket is not listening for connections.
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- ``EMFILE``: The per-process limit of open file descriptors has been
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reached.
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- ``ENFILE``: The system maximum for file descriptors has been reached.
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- ``EFAULT``: The addr parameter is not in a writable part of the user
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address space.
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- ``ENOBUFS`` or ``ENOMEM``: Not enough free memory.
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- ``EPROTO``: Protocol error.
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- ``EPERM``: Firewall rules forbid connection.
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.. c:function:: ssize_t send(int sockfd, const void *buf, size_t len, int flags);
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The ``send()`` call may be used only when the socket is
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in a connected state (so that the intended recipient is known). The only
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difference between ``send()`` and ``write()`` is the presence of
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``flags``. With ``zero`` flags parameter, ``send()`` is equivalent to
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``write()``. Also, ``send(s,buf,len,flags)`` is equivalent to
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``sendto(s,buf,len,flags,NULL,0)``.
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**Input Parameters:**
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- ``sockfd``: Socket descriptor of socket
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- ``buf``: Data to send
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- ``len``: Length of data to send
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- ``flags``: Send flags
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**Returned Value:** See ```sendto()`` <#sendto>`__.
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.. c:function:: ssize_t sendto(int sockfd, const void *buf, size_t len, int flags, \
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const struct sockaddr *to, socklen_t tolen);
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If ``sendto()`` is used on a connection-mode
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(SOCK_STREAM, SOCK_SEQPACKET) socket, the parameters to and tolen are
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ignored (and the error EISCONN may be returned when they are not NULL
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and 0), and the error ENOTCONN is returned when the socket was not
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actually connected.
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**Input Parameters:**
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- ``sockfd``: Socket descriptor of socket
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- ``buf``: Data to send
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- ``len``: Length of data to send
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- ``flags``: Send flags
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- ``to``: Address of recipient
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- ``tolen``: The length of the address structure
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**Returned Value:** On success, returns the number of characters sent.
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On error, -1 is returned, and ```errno`` <#ErrnoAccess>`__ is set
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appropriately:
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- ``EAGAIN`` or ``EWOULDBLOCK``. The socket is marked non-blocking and
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the requested operation would block.
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- ``EBADF``. An invalid descriptor was specified.
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- ``ECONNRESET``. Connection reset by peer.
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- ``EDESTADDRREQ``. The socket is not connection-mode, and no peer
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address is set.
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- ``EFAULT``. An invalid user space address was specified for a
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parameter.
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- ``EINTR``. A signal occurred before any data was transmitted.
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- ``EINVAL``. Invalid argument passed.
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- ``EISCONN``. The connection-mode socket was connected already but a
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recipient was specified. (Now either this error is returned, or the
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recipient specification is ignored.)
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- ``EMSGSIZE``. The socket type requires that message be sent
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atomically, and the size of the message to be sent made this
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impossible.
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- ``ENOBUFS``. The output queue for a network interface was full. This
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generally indicates that the interface has stopped sending, but may
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be caused by transient congestion.
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- ``ENOMEM``. No memory available.
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- ``ENOTCONN``. The socket is not connected, and no target has been
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given.
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- ``ENOTSOCK``. The argument s is not a socket.
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- ``EOPNOTSUPP``. Some bit in the flags argument is inappropriate for
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the socket type.
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- ``EPIPE``. The local end has been shut down on a connection oriented
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socket. In this case the process will also receive a SIGPIPE unless
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MSG_NOSIGNAL is set.
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.. c:function:: ssize_t recv(int sockfd, void *buf, size_t len, int flags);
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The ``recv()`` call is identical to
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```recvfrom()`` <#recvfrom>`__ with a NULL ``from`` parameter.
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**Input Parameters:**
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- sockfd: Socket descriptor of socket
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- buf: Buffer to receive data
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- len: Length of buffer
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- flags: Receive flags
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**Returned Value:** See ```recvfrom()`` <#recvfrom>`__.
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.. c:function:: ssize_t recvfrom(int sockfd, void *buf, size_t len, int flags, \
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struct sockaddr *from, socklen_t *fromlen);
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``recvfrom()`` receives messages from a socket, and may
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be used to receive data on a socket whether or not it is
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connection-oriented.
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If ``from`` is not NULL, and the underlying protocol provides the source
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address, this source address is filled in. The argument ``fromlen``
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initialized to the size of the buffer associated with ``from``, and
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modified on return to indicate the actual size of the address stored
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there.
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**Input Parameters:**
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- ``sockfd``: Socket descriptor of socket.
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- ``buf``: Buffer to receive data.
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- ``len``: Length of buffer.
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- ``flags``: Receive flags.
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- ``from``: Address of source.
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- ``fromlen``: The length of the address structure.
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**Returned Value:** On success, returns the number of characters sent.
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If no data is available to be received and the peer has performed an
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orderly shutdown, recv() will return 0. Otherwise, on errors, -1 is
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returned, and ```errno`` <#ErrnoAccess>`__ is set appropriately:
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- ``EAGAIN``. The socket is marked non-blocking and the receive
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operation would block, or a receive timeout had been set and the
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timeout expired before data was received.
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- ``EBADF``. The argument ``sockfd`` is an invalid descriptor.
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- ``ECONNREFUSED``. A remote host refused to allow the network
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connection (typically because it is not running the requested
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service).
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- ``EFAULT``. The receive buffer pointer(s) point outside the process's
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address space.
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- ``EINTR``. The receive was interrupted by delivery of a signal before
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any data were available.
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- ``EINVAL``. Invalid argument passed.
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- ``ENOMEM``. Could not allocate memory.
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- ``ENOTCONN``. The socket is associated with a connection-oriented
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protocol and has not been connected.
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- ``ENOTSOCK``. The argument ``sockfd`` does not refer to a socket.
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.. c:function:: int setsockopt(int sockfd, int level, int option, \
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const void *value, socklen_t value_len);
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``setsockopt()`` sets the option specified by the
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``option`` argument, at the protocol level specified by the ``level``
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argument, to the value pointed to by the ``value`` argument for the
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socket associated with the file descriptor specified by the ``sockfd``
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argument.
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The ``level`` argument specifies the protocol level of the option. To
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set options at the socket level, specify the level argument as
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SOL_SOCKET.
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See ``sys/socket.h`` for a complete list of values for the ``option``
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argument.
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**Input Parameters:**
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- ``sockfd``: Socket descriptor of socket
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- ``level``: Protocol level to set the option
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- ``option``: identifies the option to set
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- ``value``: Points to the argument value
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- ``value_len``: The length of the argument value
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**Returned Value:** On success, returns the number of characters sent.
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On error, -1 is returned, and ```errno`` <#ErrnoAccess>`__ is set
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appropriately:
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- ``BADF``. The ``sockfd`` argument is not a valid socket descriptor.
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- ``DOM``. The send and receive timeout values are too big to fit into
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the timeout fields in the socket structure.
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- ``INVAL``. The specified option is invalid at the specified socket
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``level`` or the socket has been shut down.
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- ``ISCONN``. The socket is already connected, and a specified option
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cannot be set while the socket is connected.
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- ``NOPROTOOPT``. The ``option`` is not supported by the protocol.
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- ``NOTSOCK``. The ``sockfd`` argument does not refer to a socket.
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- ``NOMEM``. There was insufficient memory available for the operation
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to complete.
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- ``NOBUFS``. Insufficient resources are available in the system to
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complete the call.
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.. c:function:: int getsockopt(int sockfd, int level, int option, void *value, socklen_t *value_len);
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``getsockopt()`` retrieve those value for the option
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specified by the ``option`` argument for the socket specified by the
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``sockfd`` argument. If the size of the option value is greater than
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``value_len``, the value stored in the object pointed to by the
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``value`` argument will be silently truncated. Otherwise, the length
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pointed to by the ``value_len`` argument will be modified to indicate
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the actual length of the ``value``.
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The ``level`` argument specifies the protocol level of the option. To
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retrieve options at the socket level, specify the level argument as
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SOL_SOCKET.
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See ``sys/socket.h`` for a complete list of values for the ``option``
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argument.
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**Input Parameters:**
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- ``sockfd``: Socket descriptor of socket
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- ``level``: Protocol level to set the option
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- ``option``: Identifies the option to get
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- ``value``: Points to the argument value
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- ``value_len``: The length of the argument value
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**Returned Value:** On success, returns the number of characters sent.
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On error, -1 is returned, and ```errno`` <#ErrnoAccess>`__ is set
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appropriately:
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- ``BADF``. The ``sockfd`` argument is not a valid socket descriptor.
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- ``INVAL``. The specified option is invalid at the specified socket
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``level`` or the socket has been shutdown.
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- ``NOPROTOOPT``. The ``option`` is not supported by the protocol.
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- ``NOTSOCK``. The ``sockfd`` argument does not refer to a socket.
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- ``NOBUFS``. Insufficient resources are available in the system to
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complete the call.
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