BSD Sockets#

__socklen_t#

typedef uint32_t __socklen_t

Length type for network syscalls.

socklen_t#

typedef __socklen_t socklen_t

Length type for network syscalls.

__sa_family_t#

typedef uint8_t __sa_family_t

sockaddr address family type

sa_family_t#

typedef __sa_family_t sa_family_t

sockaddr address family type

socket#

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

Create an endpoint for communication.

socket() creates an endpoint for communication and returns a file descriptor that refers to that endpoint. The file descriptor returned by a successful call will be the lowest-numbered file descriptor not currently open for the process.

Returns

• -1 is returned if an error occurs. Otherwise, the return value is a descriptor referencing the socket.

bind#

int bind (int socket_id, const struct sockaddr * addr, socklen_t addr_len)

Bind a name to a socket.

When a socket is created with socket(), it exists in a name space (address family) but has no address assigned to it.
bind() assigns the address specified by addr to the socket referred to by the file descriptor socket_id.
addrlen specifies the size, in bytes, of the address structure pointed to by addr. Traditionally, this operation is called “assigning a name to a socket”.

It is normally necessary to assign a local address using bind() before a SOCK_STREAM socket may receive connections

Returns

• The value 0 if successful. Otherwise, the value -1 is returned and the global variable errno is set to indicate the error.

listen#

int listen (int socket_id, int backlog)

Listen for connections on a socket.

listen() marks the socket referred to by socket_id as a passive socket, that is, as a socket that will be used to accept incoming connection requests using accept.

This applies only to sockets of type SOCK_STREAM or SOCK_SEQPACKET.

• Pre-conditions:

  • To accept connections, a socket is first created with socket(), a willingness to accept incoming connections and a queue limit for incoming connections are specified with listen(), and then the connections are accepted with accept().

Returns

• The value 0 if successful. Otherwise, the value -1 is returned and the global variable errno is set to indicate the error.

accept#

int accept (int socket_id, struct sockaddr * addr, socklen_t * addr_len)

Accept a connection on a socket.

The accept() system call is used with connection-based socket types (SOCK_STREAM, SOCK_SEQPACKET).
It extracts the first connection request on the queue of pending connections for the listening socket (socket_id), creates a new connected socket, and returns a new file descriptor referring to that socket.
The newly created socket is not in the listening state. The original socket sockfd is unaffected by this call.

If no pending connections are present on the queue and the original socket is not marked as non-blocking, this function blocks the caller until a connection is present. If the original socket is marked non-blocking and no pending connections are present on the queue, accept() returns an error. The accepted socket may not be used to accept more connections. The original socket socket_id remains open.

Returns

• -1 on error. If they succeed, they return a non-negative integer that is a descriptor for the accepted socket.

Note

• The accept() system call only supports blocking.

connect#

int connect (int socket_id, const struct sockaddr * addr, socklen_t addr_len)

Initiate a connection on a socket.

The connect() system call connects the socket referred to by the file descriptor sockfd to the address specified by addr.
The addrlen argument specifies the size of addr. The format of the address in addr is determined by the address space of the socket sockfd; see socket() for further details.

If socket_id is of type SOCK_DGRAM, connect() system call specifies the peer with which the socket is to be associated. If the socket is of type SOCK_STREAM, connect() system call attempts to make a connection to another socket. The other socket is specified by addr, which is an address in the communications space of the socket. Each communications space interprets the addr argument in its own way. Generally, stream sockets may successfully connect() only once; datagram sockets can use connect() multiple times to change their association.

Returns

• The value 0 if successful. Otherwise, the value -1 is returned and the global variable errno is set to indicate the error.

Note

• Connecting to an invalid address, such as null address, will result in EFAULT error.

recv#

ssize_t recv (int socket_id, void * buf, size_t buf_len, int flags)

Receive a message from a socket.

The recv() function is normally used only on a connected socket. recv() receives messages from a socket. recv() returns the length of the message on successful completion. If a message is too long to fit in the supplied buffer, excess bytes may be discarded depending on the type of socket the message is received from.

Returns

• ssize_t.

Note

• The recv() system call doesn't support any flags.

recvfrom#

ssize_t recvfrom (int socket_id, void * buf, size_t buf_len, int flags, struct sockaddr * from_addr, socklen_t * from_addr_len)

Receive a message from a socket.

The recvfrom() system calls are used to receive messages from a socket and can be used to receive data on a socket whether or not it is connection-oriented. If from_addr is not a null pointer and the socket is not connection-oriented, the source address of the message is filled in.

Returns

• ssize_t.

Note

• The recvfrom() system call doesn't support any flags.

send#

ssize_t send (int socket_id, const void * buf, size_t buf_len, int flags)

Send a message on a socket.

This may be used only when the socket is in a connected state. If the socket is connection-mode, the protocol must support implied connect or the socket must be in a connected state before use. No indication of failure to deliver is implicit in a send(). Locally detected errors are indicated by a return value of -1. If no messages space is available at the socket to hold the message to be transmitted, then send() normally blocks, unless the socket has been placed in non-blocking I/O mode.

Returns

• The number of octets sent. If an error occurred, a value of -1 is returned.

Note

• Currently, send() system call supports only blocking. The send() system call doesn't guarantee the packets are transmitted to remote note, which are enqueued in the queue. The send() system call doesn't supports any flags. The send() system call can only send max of 1460 bytes incase of plain TCP, UDP. Whereas incase of TLS, the max buffer length is 1370.

sendto#

ssize_t sendto (int socket_id, const void * buf, size_t buf_len, int flags, const struct sockaddr * to_addr, socklen_t to_addr_len)

Send a message on a socket.

The function sendto() can be used at any time if the socket is connectionless-mode. If the socket is connection-mode, the protocol must support implied connect or the socket must be in a connected state before use. The address of the target is given by to with to_addr_len specifying its size. If the socket is in a connected state, the target address passed to sendto() is ignored. If the message is too long to pass atomically through the protocol, the error EMSGSIZE is returned, and the message is not transmitted.

Returns

• The number of octets sent. If an error occurred, a value of -1 is returned.

Note

• Due to firmware limitations, sendto() system call doesn't support any flags. The sendto() system call can only send max of 1460 bytes incase of plain TCP, UDP. Whereas incase of TLS, the max buffer length is 1370.

setsockopt#

int setsockopt (int socket_id, int option_level, int option_name, const void * option_value, socklen_t option_length)

Set options on sockets.

The setsockopt() system call manipulates the options associated with a socket. Options may exist at multiple protocol levels; they are always present at the uppermost "socket" level. When manipulating socket options the level at which the option resides and the name of the option must be specified. To manipulate options at the socket level, level is specified as SOL_SOCKET. To manipulate options at any other level the protocol number of the appropriate protocol controlling the option is supplied. For example, to indicate that an option is to be interpreted by the TCP protocol, level should be set to the protocol number of TCP; The option_value and option_length arguments are used to access option values for setsockopt().

Returns

• Upon successful completion, the value 0 is returned. Otherwise, the value -1 is returned and the global variable errno is set to indicate the error.

Note

• The following are the options, which are supported currently.

  • SO_RCVTIMEO

  • SO_KEEPALIVE

  • TCP_ULP

  • SO_MAX_RETRANSMISSION_TIMEOUT_VALUE

  • IP_TOS.

getsockopt#

int getsockopt (int socket_id, int option_level, int option_name, void * option_value, socklen_t * option_length)

Get options on sockets.

The getsockopt() system call manipulates the options associated with a socket. Options may exist at multiple protocol levels; they are always present at the uppermost "socket" level. When manipulating socket options, the level at which the option resides and the name of the option must be specified. To manipulate options at the socket level, level is specified as SOL_SOCKET. To manipulate options at any other level, the protocol number of the appropriate protocol controlling the option is supplied. For example, to indicate that an option is to be interpreted by the TCP protocol, level should be set to the protocol number of TCP. For getsockopt(), they identify a buffer in which the value for the requested options are to be returned.

Returns

• Upon successful completion, the value 0 is returned. Otherwise, the value -1 is returned and the global variable errno is set to indicate the error.

Note

• The following are the options, which are supported currently.

  • SO_RCVTIMEO

  • SO_KEEPALIVE

  • TCP_ULP

  • SO_MAX_RETRANSMISSION_TIMEOUT_VALUE

  • IP_TOS.

getpeername#

int getpeername (int socket_id, struct sockaddr * name, socklen_t * name_len)

Get name of connected peer socket.

The getpeername() system call returns the name of the peer connected to socket socket_id. The name is truncated if the buffer provided is too small.

Returns

• The getpeername() function returns the value 0 if successful. Otherwise, the value -1 is returned and the global variable errno is set to indicate the error.

getsockname#

int getsockname (int socket_id, struct sockaddr * name, socklen_t * name_len)

Get socket name.

getsockname() system call returns the current name for the specified socket.

Returns

• The getsockname() function returns the value 0 if successful. Otherwise, the value -1 is returned and the global variable errno is set to indicate the error.

close#

int close (int socket_id)

Close a file descriptor.

close() closes a file descriptor, so that it no longer refers to any file and can be reused.

Returns

• The close() function returns the value 0 if successful. Otherwise, the value -1 is returned and the global variable errno is set to indicate the error.

Note

• Calling close on server or first client socket will close other sockets as well.

• Closing an non existing socket, error EBADF (Bad file descriptor) will be thrown.