Current bitcoin-master on testnet, `maxconnections=8` in the config file. Running in VM that doesn't have public IP and is not reachable from the Internet.

Wait until you have 8 peers.

```
telnet localhost 18333
```

It will result in:

```
Assertion failed: (nMaxInbound > 0), function AcceptConnection, file net.cpp, line 973.
```

First found in https://github.com/bitcoin/bitcoin/pull/8996, but can be reproduced on master.

{
        if (!IsSelectableSocket(hSocket)) {
            LogPrintf("Cannot create connection: non-selectable socket created (fd >= FD_SETSIZE ?)\n");
            CloseSocket(hSocket);
            return NULL;
        }
        if (pszDest && addrConnect.IsValid()) {
            
            
            
            
            CNode* pnode = FindNode((CService)addrConnect);
            if (pnode)
            {
                pnode->AddRef();
                {
                    LOCK(cs_vNodes);
                    if (pnode->addrName.empty()) {
                        pnode->addrName = std::string(pszDest);
                    }
                }
                CloseSocket(hSocket);
                return pnode;
            }
        }
        addrman.Attempt(addrConnect, fCountFailure);
        
        CNode* pnode = new CNode(GetNewNodeId(), nLocalServices, GetBestHeight(), hSocket, addrConnect, CalculateKeyedNetGroup(addrConnect), pszDest ? pszDest : "", false);
        GetNodeSignals().InitializeNode(pnode->GetId(), pnode);
        pnode->AddRef();