Intro(SSC) 6 January 1993 Intro(SSC) Name Intro - introduction to socket system calls and error numbers Syntax #include <sys/errno.h> Description This section describes all of the socket system calls used in SCO UNIX. All of these system calls are accessible from the socket library, lib- socket. The link editor ld(CP) and the C compiler cc(CP) search this library when the -lsocket option is specified. Most of these calls have one or more error returns, and some of the error codes are socket specfic. An error condition is indicated by an otherwise impossible return value. This is almost always -1; the individual descriptions specify the details. Note that a number of system calls overload the meanings of these error numbers, and that the meanings must be inter- preted according to the type and circumstances of the call. As with normal arguments, all return codes and values from functions are of type integer unless otherwise noted. An error number is also made available in the external variable errno, which is not cleared on suc- cessful calls. Thus errno should be tested only after an error has occurred. The following is a complete list of the socket errors and their names as given in <sys/errno.h>. See Intro(S) for a more comprehensive list of error codes. 63 ENOBUFS No buffer space available An operation on a socket or pipe was not performed because the system lacked sufficient buffer space or because a queue was full. ENOBUFS is defined to have the same value as ENOSR. 90 TCPERR The starting value of socket related error codes. TCPERR+0 EWOULDBLOCK Operation would block An operation that would cause a process to block was attempted on an object in non-blocking mode (see fcntl(SSC)). TCPERR+1 EINPROGRESS Operation now in progress An operation that takes a long time to complete (such as a connect(SSC)) was attempted on a non-blocking object (see fcntl(SSC)). TCPERR+2 EALREADY Operation already in progress An operation was attempted on a non-blocking object that already had an operation in progress. TCPERR+3 ENOTSOCK Socket operation on non-socket Self-explanatory. TCPERR+4 EDESTADDRREQ Destination address required A required address was omitted from an operation on a socket. TCPERR+5 EMSGSIZE Message too long A message sent on a socket was larger than the internal message buffer or some other network limit. TCPERR+6 EPROTOTYPE Protocol wrong type for socket A protocol was specified that does not support the semantics of the socket type requested. For example, you cannot use the ARPA Internet UDP protocol with type SOCKSTREAM. TCPERR+7 EPROTONOSUPPORT Protocol not supported The protocol has not been configured into the system or no implementa- tion for it exists. TCPERR+8 ESOCKTNOSUPPORT Socket type not supported The support for the socket type has not been configured into the sys- tem or no implementation for it exists. TCPERR+9 EOPNOTSUPP Operation not supported on socket For example, trying to accept a connection on a datagram socket. TCPERR+10 EPFNOSUPPORT Protocol family not supported The protocol family has not been configured into the system or no implementation for it exists. TCPERR+11 EAFNOSUPPORT Address family not supported by protocol family An address incompatible with the requested protocol was used. For example, you shouldn't necessarily expect to be able to useNS addresses with ARPA Internet protocols. TCPERR+12 EADDRINUSE Address already in use Only one usage of each address is normally permitted. TCPERR+13 EADDRNOTAVAIL Can't assign requested address Normally results from an attempt to create a socket with an address not on this machine. TCPERR+14 ENETDOWN Network is down A socket operation encountered a dead network. TCPERR+15 ENETUNREACH Network is unreachable A socket operation was attempted to an unreachable network. TCPERR+16 ENETRESET Network dropped connection on reset The host you were connected to crashed and rebooted. TCPERR+17 ECONNABORTED Software caused connection abort A connection abort was caused internal to your host machine. TCPERR+18 ECONNRESET Connection reset by peer A connection was forcibly closed by a peer. This normally results from a loss of the connection on the remote socket due to a timeout or a reboot. TCPERR+19 unused TCPERR+20 EISCONN Socket is already connected A connect request was made on an already connected socket; or, a sendto or sendmsg request on a connected socket specified a destina- tion when already connected. TCPERR+21 ENOTCONN Socket is not connected An request to send or receive data was disallowed because the socket is not connected and (when sending on a datagram socket) no address was supplied. TCPERR+22 ESHUTDOWN Can't send after socket shutdown A request to send data was disallowed because the socket had already been shut down with a previous shutdown(SSC) call. TCPERR+23 unused TCPERR+24 ETIMEDOUT Connection timed out A connect or send request failed because the connected party did not properly respond after a period of time. (The timeout period is dependent on the communication protocol.) TCPERR+25 ECONNREFUSED Connection refused No connection could be made because the target machine actively refused it. This usually results from trying to connect to a service that is inactive on the foreign host. TCPERR+26 EHOSTDOWN Host is down A socket operation failed because the destination host was down. TCPERR+27 EHOSTUNREACH Host is unreachable A socket operation was attempted to an unreachable host. TCPERR+28 ENOPROTOOPT Option not supported by protocol A bad option or level was specified in a getsockopt(SSC) or setsockopt(SSC) call. Files /usr/lib/libsocket.a Definitions Socket Descriptor An integer assigned by the system when a socket is referenced by dup(S), or when a socket is created by socket(SSC), which uniquely identifies an access path to that socket from a given process or any of its children. Sockets and Address Families A socket is an endpoint for communication between processes. Each socket has queues for sending and receiving data. Sockets are typed according to their communications properties. These properties include whether messages sent and received at a socket require the name of the partner, whether communication is reliable, the format used in naming message recipients, etc. Each instance of the system supports some collection of socket types; consult socket(SSC) for more information about the types available and their properties. Each instance of the system supports some number of sets of communi- cations protocols. Each protocol set supports addresses of a cer- tain format. An Address Family is the set of addresses for a spe- cific group of protocols. Each socket has an address chosen from the address family in which the socket was created. List of functions __________________________________________________________________________ Name Appears on Page Description __________________________________________________________________________ accept accept(SSC) accept a connection on a socket adjtime adjtime(SSC) correct system time to network average bind bind(SSC) bind a name to a socket connect connect(SSC) initiate a connection on a socket getpeername getpeername(SSC) get name of connected peer getsockname getsockname(SSC) get socket name getsockopt getsockopt(SSC) get options on sockets gettimeofday gettimeofday(SSC) get date and time listen listen(SSC) listen for connections on a socket recv recv(SSC) receive a message from a connected socket recvfrom recv(SSC) receive a message from a socket send send(SSC) send a message to a connected socket sendto send(SSC) send a message to a socket setsockopt getsockopt(SSC) set options on sockets settimeofday gettimeofday(SSC) set date and time shutdown shutdown(SSC) shut down part of a full-duplex connection socket socket(SSC) create an endpoint for communication See also Intro(S) and perror(S).