socket() Create an endpoint for communication int socket( int
domain, int type, int protocol ); domain PF_INET for IPv4 PF_INET6
for IPv6 type SOCK_STREAM for reliable TCP sockets SOCK_DGRAM for
unreliable fast UDP sockets protocol default: 0 5
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bind() Bind a name to a socket int bind( int s, const struct
sockaddr * name, socklen_t namelen ); s The file descriptor to be
bound. name A pointer to the sockaddr structure that holds the
address to be bound to the socket. namelen The length of the
sockaddr structure pointed to by name. 6
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bind() (con.) struct sockaddr { sa_family_t sa_family; //
address family, AF_xxx char sa_data[14]; // 14 bytes of protocol
address }; sa_family represents address family sa_data contains
data about address 7
listen() Listen for connections on a socket int listen( int s,
int backlog ); s The descriptor for the socket that you want to
listen on. backlog The maximum length that the queue of pending
connections may grow to. 10
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connect() Initiate a connection on a socket int connect( int s,
const struct sockaddr * name, socklen_t namelen ); s The descriptor
of the socket on which to initiate the connection. name The name of
the socket to connect to for a SOCK_STREAM connection. namelen The
length of the name, in bytes. 11
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accept() Accept a connection on a socket int accept( int s,
struct sockaddr * addr, socklen_t * addrlen ); s The listen()ing
socket descriptor. addr This is filled in with the address of the
site that's connecting to you. addrlen This is filled in with the
sizeof() the structure returned in the addr parameter. You can
safely ignore it if you assume you're getting a struct sockaddr_in
back, which you know you are, because that's the type you passed in
for addr. 12
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send() Send a message to a connected socket ssize_t send( int
s, const void * msg, size_t len, int flags ); msg A pointer to the
message that you want to send. len The length of the message. flags
Set flags to zero if you want it to be "normal" data. 13
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recv() Receive a message from a socket ssize_t recv( int s,
void * buf, size_t len, int flags ); buf A pointer to a buffer
where the function can store the message. len The size of the
buffer. flags Set flags to 0 if you want it to be a regular vanilla
recv(). 14
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close() Close a socket descriptor int close(int s); Windows
users: the function you need to use is called closesocket(), not
close(). 15
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Connectionless socket (UDP) 16
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sendto() Send a message to a socket at a specific address
ssize_t sendto( int s, const void * msg, size_t len, int flags,
const struct sockaddr * to, socklen_t tolen ); to A pointer to a
sockaddr object that specifies the address of the target. tolen A
socklen_t object that specifies the size of the to address. 17
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recvfrom() Receive a message from the socket at a specified
address ssize_t recvfrom( int s, void * buff, size_t len, int
flags, struct sockaddr * from, socklen_t * fromlen ); from NULL, or
a pointer to a sockaddr object where the function can store the
source address of the message. fromlen A pointer to a socklen_t
object that specifies the size of the from buffer. The function
stores the actual size of the address in this object. 18
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inet_ntop() inet_pton() Convert IP addresses to human-readable
form and back const char *inet_ntop(int af, const void *src, char
*dst, socklen_t size); int inet_pton(int af, const char *src, void
*dst); The "n" stands for "network", and "p" for "presentation".
These functions are for dealing with human-readable IP addresses
and converting them to their binary representation for use with
various functions and system calls. 19
htons() htonl() ntohs() ntohl() Convert multi-byte integer
types from host byte order to network byte order uint32_t
htonl(uint32_t hostlong); uint16_t htons(uint16_t hostshort);
uint32_t ntohl(uint32_t netlong); uint16_t ntohs(uint16_t
netshort); htons()host to network short htonl()host to network long
ntohs()network to host short ntohl()network to host long 24
