good resource for socket errors?

Question

Where can I find a list of all types of bsd style socket errors?

Answer 1

You can also find a list of error codes (and a general description of their meaning) on the Open Group's pages for each function (like connect, for example).

Answer 2

In the documentation? For instance, for connect(), see:

% man connect
...
  ECONNREFUSED
          No-one listening on the remote address.
  EISCONN
          The socket is already connected.

  ENETUNREACH
          Network is unreachable.

Answer 3

Of you want to know all possible errno's or some comments on them you could take a look at the header files, on a Linux system there are located in

• /usr/include/asm-generic/errno-base.h

#ifndef _ASM_GENERIC_ERRNO_BASE_H
#define _ASM_GENERIC_ERRNO_BASE_H

#define EPERM   1 /* Operation not permitted */
#define ENOENT   2 /* No such file or directory */
#define ESRCH   3 /* No such process */
#define EINTR   4 /* Interrupted system call */
#define EIO   5 /* I/O error */
#define ENXIO   6 /* No such device or address */
#define E2BIG   7 /* Argument list too long */
#define ENOEXEC   8 /* Exec format error */
#define EBADF   9 /* Bad file number */
#define ECHILD  10 /* No child processes */
#define EAGAIN  11 /* Try again */
...

• /usr/include/asm-generic/errno.h

#ifndef _ASM_GENERIC_ERRNO_H
#define _ASM_GENERIC_ERRNO_H

#include 

#define EDEADLK  35 /* Resource deadlock would occur */
#define ENAMETOOLONG 36 /* File name too long */
#define ENOLCK  37 /* No record locks available */
#define ENOSYS  38 /* Function not implemented */
#define ENOTEMPTY 39 /* Directory not empty */
#define ELOOP  40 /* Too many symbolic links encountered */
#define EWOULDBLOCK EAGAIN /* Operation would block */
...

If you want to know what errno a call, e.g. socket() or connect() can return, when install the development manpages and try man socket or man connect

Answer 4

Many functions will set errno on failure, and instead of going through errno.h yourself and converting the error number to strings, you are much better off calling perror.

perror will print the current errno's corresponding message to stderr with an optional prefix.

Example usage:

if (connect())
{
    perror("connect() failed in function foo");
    ...
}

perror has friends called strerror and strerror_r who might prove useful if you want to capture the string for use in places other than stderr.