我的 C++ 应用程序在从 32 位 Linux 移植到 32 位 FreeBSD 8.1 时出现故障。我有一个无法连接的 TCP 套接字连接。在对 connect() 的调用中，我得到了一个错误结果，错误结果为 errno == EINVAL，connect() 的手册页没有涵盖该结果。
这个错误是什么意思，哪个参数无效？消息只是说：“无效参数”。
以下是连接的一些细节：
family: AF_INET
len: 16
port: 2357
addr: 10.34.49.13
但它并不总是失败。FreeBSD 版本只有在让机器闲置几个小时后才会失败。但是在失败一次之后，它可以可靠地工作，直到您让它再次闲置很长一段时间。
这是一些代码：
void setSocketOptions(const int skt);
void buildAddr(sockaddr_in &addr, const std::string &ip,
const ushort port);
void deepBind(const int skt, const sockaddr_in &addr);
void
test(const std::string &localHost, const std::string &remoteHost,
const ushort localPort, const ushort remotePort,
sockaddr_in &localTCPAddr, sockaddr_in &remoteTCPAddr)
{
const int skt = socket(AF_INET, SOCK_STREAM, 0);
if (0 > skt) {
clog << "Failed to create socket: (errno " << errno
<< ") " << strerror(errno) << endl;
throw;
}
setSocketOptions(skt);
// Build the localIp address and bind it to the feedback socket. Although
// it's not traditional for a client to bind the sending socket to a the
// local address, we do it to prevent connect() from using an ephemeral port
// which (our site's firewall may block). Also build the remoteIp address.
buildAddr(localTCPAddr, localHost, localPort);
deepBind(skt, localTCPAddr);
buildAddr(remoteTCPAddr, remoteHost, remotePort);
clog << "Info: Command connect family: "
<< (remoteTCPAddr.sin_family == AF_INET ? "AF_INET" : "<unknown>")
<< " len: " << int(remoteTCPAddr.sin_len)
<< " port: " << ntohs(remoteTCPAddr.sin_port)
<< " addr: " << inet_ntoa(remoteTCPAddr.sin_addr) << endl;
if (0 > ::connect(skt, (sockaddr*)& remoteTCPAddr, sizeof(sockaddr_in)))) {
switch (errno) {
case EINVAL: {
int value = -1;
socklen_t len = sizeof(value);
getsockopt(skt, SOL_SOCKET, SO_ERROR, &value, &len);
cerr << "Error: Command connect failed on local port "
<< getLocFbPort()
<< " and remote port " << remotePort
<< " to remote host '" << remoteHost
<< "' family: "
<< (remoteTCPAddr.sin_family == AF_INET ? "AF_INET" : "<unknown>")
<< " len: " << int(remoteTCPAddr.sin_len)
<< " port: " << ntohs(remoteTCPAddr.sin_port)
<< " addr: " << inet_ntoa(remoteTCPAddr.sin_addr)
<< ": Invalid argument." << endl;
cerr << "\tgetsockopt => "
<< ((value != 0) ? strerror(value): "success") << endl;
throw;
}
default: {
cerr << "Error: Command connect failed on local port "
<< localPort << " and remote port " << remotePort
<< ": (errno " << errno << ") " << strerror(errno) << endl;
throw;
}
}
}
}
void
setSocketOptions(int skt)
{
// See page 192 of UNIX Network Programming: The Sockets Networking API
// Volume 1, Third Edition by W. Richard Stevens et. al. for info on using
// ::setsockopt().
// According to "Linux Socket Programming by Example" p. 319, we must call
// setsockopt w/ SO_REUSEADDR option BEFORE calling bind.
int so_reuseaddr = 1; // Enabled.
int reuseAddrResult
= ::setsockopt(skt, SOL_SOCKET, SO_REUSEADDR, &so_reuseaddr,
sizeof(so_reuseaddr));
if (reuseAddrResult != 0) {
cerr << "Failed to set reuse addr on socket.";
throw;
}
// For every two hours of inactivity, a keepalive occurs.
int so_keepalive = 1; // Enabled. See page 200 for info on SO_KEEPALIVE.
int keepAliveResult =
::setsockopt(skt, SOL_SOCKET, SO_KEEPALIVE, &so_keepalive,
sizeof(so_keepalive));
if (keepAliveResult != 0) {
cerr << "Failed to set keep alive on socket.";
throw;
}
struct linger so_linger;
so_linger.l_onoff = 1; // Turn linger option on.
so_linger.l_linger = 5; // Linger time in seconds. (See page 202)
int lingerResult
= ::setsockopt(skt, SOL_SOCKET, SO_LINGER, &so_linger,
sizeof(so_linger));
if (lingerResult != 0) {
cerr << "Failed to set linger on socket.";
throw;
}
// Disable the Nagel algorithm on the command channel. SOL_TCP is not
// defined on FreeBSD
#ifndef SOL_TCP
#define SOL_TCP (::getprotobyname("TCP")->p_proto)
#endif
unsigned int tcpNoDelay = 1;
int noDelayResult
= ::setsockopt(skt, SOL_TCP, TCP_NODELAY, &tcpNoDelay,
sizeof(tcpNoDelay));
if (noDelayResult != 0) {
cerr << "Failed to set tcp no delay on socket.";
throw;
}
}
void
buildAddr(sockaddr_in &addr, const std::string &ip, const ushort port)
{
memset(&addr, 0, sizeof(sockaddr_in)); // Clear all fields.
addr.sin_len = sizeof(sockaddr_in);
addr.sin_family = AF_INET; // Set the address family
addr.sin_port = htons(port); // Set the port.
if (0 == inet_aton(ip.c_str(), &addr.sin_addr)) {
cerr << "BuildAddr IP.";
throw;
}
};
void
deepBind(const int skt, const sockaddr_in &addr)
{
// Bind the requested port.
if (0 <= ::bind(skt, (sockaddr *)&addr, sizeof(addr))) {
return;
}
// If the port is already in use, wait up to 100 seconds.
int count = 0;
ushort port = ntohs(addr.sin_port);
while ((errno == EADDRINUSE) && (count < 10)) {
clog << "Waiting for port " << port << " to become available..."
<< endl;
::sleep(10);
++count;
if (0 <= ::bind(skt, (sockaddr*)&addr, sizeof(addr))) {
return;
}
}
cerr << "Error: failed to bind port.";
throw;
}
这是 EINVAL 时的示例输出（它并不总是在这里失败，有时它会成功并在通过套接字发送的第一个数据包被加扰时失败）：
Info: Command connect family: AF_INET len: 16 port: 2357 addr: 10.34.49.13
Error: Command connect failed on local port 2355 and remote port 2357 to remote host '10.34.49.13' family: AF_INET len: 16 port: 2357 addr: 10.34.49.13: Invalid argument.
getsockopt => success