ACCEPT(2) 1990 ACCEPT(2) NNAAMMEE accept - accept a connection on a socket SSYYNNOOPPSSIISS ##iinncclluuddee <<ssyyss//ttyyppeess..hh>> ##iinncclluuddee <<ssyyss//ssoocckkeett..hh>> nnss == aacccceepptt((ss,, aaddddrr,, aaddddrrlleenn)) iinntt nnss,, ss;; ssttrruucctt ssoocckkaaddddrr **aaddddrr;; iinntt **aaddddrrlleenn;; DDEESSCCRRIIPPTTIIOONN The argument _s is a socket that has been created with _s_o_c_k_e_t(2), bound to an address with _b_i_n_d(2), and is listen- ing for connections after a _l_i_s_t_e_n(2). _A_c_c_e_p_t extracts the first connection request on the queue of pending connec- tions, creates a new socket with the same properties of _s and allocates a new file descriptor, _n_s, for the socket. If no pending connections are present on the queue, and the socket is not marked as non-blocking, _a_c_c_e_p_t blocks the caller until a connection is present. If the socket is marked non-blocking and no pending connections are present on the queue, _a_c_c_e_p_t returns an error as described below. The accepted socket, _n_s, may not be used to accept more con- nections. The original socket _s remains open. The argument _a_d_d_r is a result parameter that is filled in with the address of the connecting entity, as known to the communications layer. The exact format of the _a_d_d_r parame- ter is determined by the domain in which the communication is occurring. The _a_d_d_r_l_e_n is a value-result parameter; it should initially contain the amount of space pointed to by _a_d_d_r; on return it will contain the actual length (in bytes) of the address returned. This call is used with connection-based socket types, currently with SOCK_STREAM. It is possible to _s_e_l_e_c_t(2) a socket for the purposes of doing an _a_c_c_e_p_t by selecting it for read. For certain protocols which require an explicit confirma- tion, such as ISO or DATAKIT, one should think of accept as merely dequeueing the next connection request, and not in of itself implying confirmation. Confirmation can be implied by a normal read or write on the new file desciptor, and rejection can be implied by closing the new socket. One can obtain user connection request data without confirm- ing the connection by issuing a recvmsg call with an msg_iovlen of 0 and a non-zero msg_controllen, or by issuing a _g_e_t_s_o_c_k_o_p_t(2) request. Similarly, one can provide user connection rejection information by issuing a sendmsg call Printed 7/27/90 May 1 ACCEPT(2) 1990 ACCEPT(2) with providing only the control information, or by calling _s_e_t_s_o_c_k_o_p_t(2). RREETTUURRNN VVAALLUUEE The call returns -1 on error. If it succeeds, it returns a non-negative integer that is a descriptor for the accepted socket. EERRRROORRSS The _a_c_c_e_p_t will fail if: [EBADF] The descriptor is invalid. [ENOTSOCK] The descriptor references a file, not a socket. [EOPNOTSUPP] The referenced socket is not of type SOCK_STREAM. [EFAULT] The _a_d_d_r parameter is not in a writable part of the user address space. [EWOULDBLOCK] The socket is marked non-blocking and no connections are present to be accepted. SSEEEE AALLSSOO bind(2), connect(2), listen(2), select(2), socket(2) Printed 7/27/90 May 2