Linux system call: getaddrinfo return -2

Question

I'm using the system call getaddrinfo and it return -2. I try to know what is this error and get that ths is "name or service not known". the name - it is my host name and I'm sure it is known. but the service is a number that is changed from run to run. how can I know that I am bringing the correct parameter? my code: ``` int GetSockPeerIPs(int sock, AddressList &addresses, int &error, int family, bool zeroport) { struct sockaddr_storage ss; socklen_t salen = sizeof(ss); struct sockaddr *sa; struct addrinfo hints, *paddr, *paddrp; sa = (struct sockaddr *)&ss; if (getpeername(sock, sa, &salen) != 0) { error = errno; return -1; } char hbuf[NI_MAXHOST]; char pbuf[NI_MAXSERV]; if (0 != (error = getnameinfo(sa, salen, hbuf, sizeof(hbuf), pbuf, sizeof(pbuf), 0))) { return -1; } memset(&hints, 0, sizeof(hints)); if (ATNetworkTool::AF_XINETX == family) { hints.ai_family = PF_UNSPEC; } else { hints.ai_family = family; } hints.ai_socktype = SOCK_STREAM; if (0 != (error = getaddrinfo(hbuf, pbuf…

Accepted Answer

You have an error code. Have you thought about finding out what it means? On this occasion I have done it for you. But here's what I did so you can look it up for yourself next time.

Looking at the man page for getaddrinfo() I found it can return a number of error codes e.g. EAI_AGAIN. The numeric values will be defined in a header file somewhere, so I did

```
cd /usr/include
find . -name "*.h" -exec grep -l EAI_AGAIN {} \;
```

This identified netdb.h. So I opened that in vi and this is what it said:

```
# define EAI_BADFLAGS     -1    /* Invalid value for `ai_flags' field.  */
# define EAI_NONAME       -2    /* NAME or SERVICE is unknown.  */
# define EAI_AGAIN        -3    /* Temporary failure in name resolution.  */
# define EAI_FAIL         -4    /* Non-recoverable failure in name res.  */
# define EAI_FAMILY       -6    /* `ai_family' not supported.  */
# define EAI_SOCKTYPE     -7    /* `ai_socktype' not supported.  */
# define EAI_SERVICE      -8    /* SERVICE not supported for `ai_socktype'.  */
# define EAI_MEMORY       -10   /* Memory allocation failure.  */
# define EAI_SYSTEM       -11   /* System error returned in `errno'.  */
# define EAI_OVERFLOW     -12   /* Argument buffer overflow.  */
```

So basically, the name or service that you are passing in is unknown to getaddrinfo. I'd check to see whether the first two parameters are reasonable, if I were you.

Linux system call: getaddrinfo return -2

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