CODEWITHSUNDEEP
c++socketsudpipbind
jacknad
jacknad

Reputation: 13739

How to fix 'Cannot assign requested address?'

Both the IP address and Port are confirmed not used by netstat -a -n. When I use gdb and break in the method calling bind I see that the correct IP address and Port are being used along with a reasonable socket address length of 16. This is for a UDP Listener. The remote IP is static and read from a configuration file.

This is the code,

void CSocket::Bind(IpEndPoint& endPoint)
{
    int bindResult = bind( socketHandle, endPoint.GetSockAddrPtr(), 
        endPoint.GetAddrLength());
    if(bindResult < 0)
    {
        TRACE_ERROR("Failed to bind to socket. %s. IpAddress %s Port %d AddrLength %d",
            strerror(errno), endPoint.GetIpAddressString(), 
            ntohs(endPoint.GetPort()), endPoint.GetAddrLength());

this is from gdb,

Breakpoint 1, CSocket::Bind (this=0x819fa24, ipAddress="192.0.2.77", port=4185) at Socket.cpp:126

and this is the TRACE_ERROR from the code above

ERROR: Failed to bind to socket. errno 99 (Cannot assign requested address). IpAddress 192.0.2.77 Port 4185 AddrLength 16

I've been re-reading Beej's Guide to Network Programming but not finding a clue. This is UDP so a connection should not be required to bind. The firewall is off. Where else should I be looking?

Upvotes: 2

Views: 24965

Answers (1)

Armali
Armali

Reputation: 19395

Following on what @Aconcagua said: You want to bind an address that is local (not one that's "not in use"). You can't just make up a local address. You either use INADDR_ANY to bind to any address, or you need to bind one that is assigned to one of your local interfaces. This is likely the problem. (bind sets the local address, connect sets the remote address -- or, with UDP, you can specify the remote address per packet with sendto.) – Gil Hamilton

Upvotes: 2

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