我正在编写一个简单的UDP客户端服务器聊天，以便更熟悉网络编程。现在，让用户更容易看到服务器IP地址是什么（因此用户可以将其键入客户端进行连接）。这就是为什么我希望服务器显示自己的本地IP地址。
这是我的代码：（编辑处理多个IP的代码）
// get the hostname of the server
char hostname[128];
if (gethostname(hostname, sizeof(hostname)) == -1) {
std::cout << "Could not get the hostname of the server. Error: " << std::strerror(errno) << std::endl;
return 1;
}
struct addrinfo hints, *serverInfo, *p;
std::memset(&hints, 0, sizeof(hints));
hints.ai_family = AF_UNSPEC; // use AF_INET (IPv4) or AF_INET6 (IPv6) to force version
hints.ai_socktype = SOCK_DGRAM;
// try to get information about our hostname
int rv;
if ((rv = getaddrinfo(hostname, NULL, &hints, &serverInfo)) != 0) {
std::cout << "Failed to get information about the host \"" << hostname << "\". Error: " << gai_strerror(rv) << std::endl;
return 1;
}
std::cout << "IP addresses for " << hostname << ":" << std::endl;
// iterate over all the infos we got and try to extract the IP address
for(p = serverInfo; p != NULL; p = p->ai_next) {
char serverIPAddress[INET6_ADDRSTRLEN];
void *addr;
std::string ipVersion;
// get the pointer to the address itself,
// different fields in IPv4 and IPv6:
if (p->ai_family == AF_INET) { // IPv4
struct sockaddr_in *ipv4 = (struct sockaddr_in *)p->ai_addr;
addr = &(ipv4->sin_addr);
ipVersion = "IPv4";
} else { // IPv6
struct sockaddr_in6 *ipv6 = (struct sockaddr_in6 *)p->ai_addr;
addr = &(ipv6->sin6_addr);
ipVersion = "IPv6";
}
// take the IP address of our hostname and convert it into a readable format
inet_ntop(p->ai_family, addr, serverIPAddress, sizeof(serverIPAddress));
std::cout << " " << ipVersion << ": " << serverIPAddress << std::endl;
}
freeaddrinfo(serverInfo); // free the linked list
它可以工作，但它不会显示正确的IP地址。每次我运行它时都会显示一个不同的IP，这不是正确的IP。正如我所说，我仍在学习网络编程，所以我不知道为什么会这样。有人能指出我正确的方向吗？
答案 0 :(得分：0)
您将无法获得此类“全局”IP地址，只能获取本地IP地址。为了让客户端连接到您，它需要全局IP地址，这可以从Internet上看到，即您的网关（路由器）IP。这是因为您的路由器将计算机的IP地址转换为全局可见的IP地址并将其存储在表中，以便可以将传入连接正确路由到正确的子网。这称为 NAT ing（了解有关 NAT here的更多信息）。
如果您希望客户端连接显式，您需要为其提供路由器的IP地址（根据您的操作系统使用命令行工具）并配置端口转发，路由器将自动转发到达的数据包（IP_router，port_router）到（IP_host，port_host）。这是在路由器的配置面板中完成的。根据您的路由器，这将在菜单中的某处找到。您可以通过键入192.068.0.1或192.168.0.0等内容来连接到路由器。
答案 1 :(得分：0)
在Windows上，您可以使用gethostbyname并枚举hostent h_addr_list ...在Linux上，您可以创建一个临时套接字并在ioctl上使用SIOCGIFCONF并通过接口枚举。
答案 2 :(得分：0)
// Get a Vector of the IP addresses of this computer
std::vector<std::string> getIPAddresses() {
std::vector<std::string> IPAddresses;
int TempAddress = 0;
char* TempIPAddress = (char*) malloc(16);
ifaddrs* ifap = NULL; //Head of the interface address linked list
if (getifaddrs(&ifap) == 0 && ifap != NULL) {
//Get another pointer to move down the linked list
ifaddrs* current = ifap;
//Move down the linked list until we get to a NULL pointer
while (current != NULL) {
//Create a pointer of the correct type to work with
const sockaddr_in* interfaceAddress = reinterpret_cast<const sockaddr_in*>(current->ifa_addr);
if (current->ifa_addr != NULL) {
if (current->ifa_addr->sa_family == AF_INET) {
//printf("%s:", current->ifa_name);
if (interfaceAddress != NULL) {
TempAddress = ntohl(interfaceAddress->sin_addr.s_addr);
sprintf(TempIPAddress, "%d.%d.%d.%d", (TempAddress >> 24) & 0xFF, (TempAddress >> 16) & 0xFF,
(TempAddress >> 8) & 0xFF, TempAddress & 0xFF);
//Don't include the lookback address
if (strcmp(TempIPAddress, "127.0.0.1") != 0) {
IPAddresses.push_back(std::string(TempIPAddress));
}
//printf("%s\n", TempIPAddress);
}
}
}
//Move to the next node in the linked-list
current = current->ifa_next;
}
//Release the interface memory
freeifaddrs(ifap);
ifap = NULL;
}
return IPAddresses;
}
答案 3 :(得分：0)
我认为在代码结束时，您滥用了数据结构sockaddr_in。 这一行：
inet_ntop(AF_INET, &(serverInfo->ai_addr), serverIPAddress, INET_ADDRSTRLEN);
应替换为：
struct sockaddr_in *ipv4 = (struct sockaddr_in *)serverInfo->ai_addr;
void *addr = &(ipv4->sin_addr);
inet_ntop(AF_INET, addr, serverIPAddress, INET_ADDRSTRLEN);
答案 4 :(得分：0)
Soo，感谢我在这里得到的建议，我改变了我的方法，而不是尝试将我的机器的主机名解析为IP地址，我现在简单地列出所有网络接口及其IP地址。
这是我的代码：
// get the hostname of the server
char hostname[128];
if (gethostname(hostname, sizeof(hostname)) == -1) {
std::cout << "Could not get the hostname of the server. Error: " << std::strerror(errno) << std::endl;
return 1;
}
std::cout << "IP addresses for " << hostname << ":" << std::endl << std::endl;
struct ifaddrs *networkInterfaceList, *p;
getifaddrs (&networkInterfaceList); // get information about the network interfaces
// iterate over all the network interfaces we got and try to extract their IP address
for (p = networkInterfaceList; p != NULL; p = p->ifa_next) {
char serverIPAddress[INET6_ADDRSTRLEN];
void *addr;
std::string ipVersion;
// get the pointer to the address itself,
// different fields in IPv4 and IPv6:
if (p->ifa_addr->sa_family == AF_INET) { // IPv4
struct sockaddr_in *ipv4 = (struct sockaddr_in *)p->ifa_addr;
addr = &(ipv4->sin_addr);
ipVersion = "IPv4";
} else { // IPv6
struct sockaddr_in6 *ipv6 = (struct sockaddr_in6 *)p->ifa_addr;
addr = &(ipv6->sin6_addr);
ipVersion = "IPv6";
}
// take the IP address of our hostname and convert it into a readable format
inet_ntop(p->ifa_addr->sa_family, addr, serverIPAddress, sizeof(serverIPAddress));
// sometime the IP address is empty so only print if there is one
if (std::strlen(serverIPAddress) > 0)
std::cout << "Interface: " << std::setw(6) << std::left << p->ifa_name << " " << ipVersion << ": " << serverIPAddress << std::endl;
}
freeifaddrs(networkInterfaceList); // free the linked list
以防万一其他人正在尝试类似的东西。
如果有人对此感兴趣，请访问聊天：https://github.com/Foaly/Chat