我已经调整了来自http://beej.us/guide/bgnet/output/html/singlepage/bgnet.html（selectserver.c - 一个cheezy multiperson聊天服务器）的代码，以便在Windows上进行编译。完整的代码如下。我使用gcc版本6.1.0（x86_64-posix-seh，由MinGW-W64项目构建）编译。我也在Linux上使用gcc6.1.0编译。
基本上，你运行它，telnet 2次或更多次到端口9034，你在一个telnet会话中输入的任何内容都会回显到其他telnet会话（取决于系统，必须键入 Enter 在它被回应之前 - 在Windows上它回应每个输入的字符。）
现在出现问题：
在Linux AMD64或ARM上，我可以从localhost和其他系统连接到它，无论是Windoes还是Linux。在Windows上，它只适用于localhost，我不明白为什么。如果我正确理解了事情，那么指定hints.ai_flags = AI_PASSIVE;的事实使得它可以监听所有接口。
MSDN doc州：
设置AI_PASSIVE标志表示调用者打算在调用bind函数时使用返回的套接字地址结构。
当设置AI_PASSIVE标志且pNodeName为NULL指针时，套接字地址结构的IP地址部分设置为INADDR_ANY表示IPv4地址，IN6ADDR_ANY_INIT表示IPv6地址。
代码为：
hints.ai_flags = AI_PASSIVE;
if ((rv = getaddrinfo(NULL, PORT, &hints, &ai)) != 0)
如何在Windows上正确运行？
编译时使用：
g ++ -O0 -g3 -Wall -c -fmessage-length = 0 -o＆＃34; src \ chatserver.o＆＃34; ＆＃34; .. \ SRC \ chatserver.cpp＆＃34;
并与
相关联g ++ -mwindows -o chatserver.exe＆＃34; src \ chatserver.o＆＃34; -lws2_32
我需要在代码中更改哪些内容？
这是完整的代码：
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#ifdef __linux__
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#endif
#ifdef _WIN32
#include <ws2tcpip.h>
#endif
#define PORT "9034" // port we're listening on
// get sockaddr, IPv4 or IPv6:
void *get_in_addr(struct sockaddr *sa)
{
if (sa->sa_family == AF_INET) { return &(((struct sockaddr_in*)sa)->sin_addr); }
return &(((struct sockaddr_in6*)sa)->sin6_addr);
}
int main(void)
{
#ifdef _WIN32
WSADATA wsaData; // Initialize Winsock
int nResult = WSAStartup(MAKEWORD(2,2), &wsaData);
if (NO_ERROR != nResult) {
printf ("Error occurred while executing WSAStartup().");
}
#endif
fd_set master; // master file descriptor list
fd_set read_fds; // temp file descriptor list for select()
int fdmax; // maximum file descriptor number
int listener; // listening socket descriptor
int newfd; // newly accept()ed socket descriptor
struct sockaddr_storage remoteaddr; // client address
socklen_t addrlen;
char buf[256]; // buffer for client data
int nbytes;
char remoteIP[INET6_ADDRSTRLEN];
int yes=1; // for setsockopt() SO_REUSEADDR, below
int i, j, rv;
struct addrinfo hints, *ai, *p;
FD_ZERO(&master); // clear the master and temp sets
FD_ZERO(&read_fds);
// get us a socket and bind it
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
hints.ai_flags = AI_PASSIVE;
if ((rv = getaddrinfo(NULL, PORT, &hints, &ai)) != 0) {
fprintf(stderr, "selectserver: %s\n", gai_strerror(rv));
exit(1);
}
for(p = ai; p != NULL; p = p->ai_next) {
listener = socket(p->ai_family, p->ai_socktype, p->ai_protocol);
if (listener < 0) { continue; }
// lose the pesky "address already in use" error message
setsockopt(listener, SOL_SOCKET, SO_REUSEADDR, (const char *)&yes, sizeof(int));
//setsockopt(listener, SOL_SOCKET, SO_REUSEADDR, "1", sizeof(int));
if (bind(listener, p->ai_addr, p->ai_addrlen) < 0) {
close(listener);
continue;
}
break;
}
// if we got here, it means we didn't get bound
if (p == NULL) {
fprintf(stderr, "selectserver: failed to bind\n");
exit(2);
}
freeaddrinfo(ai); // all done with this
// listen
if (listen(listener, 10) == -1) {
perror("listen");
exit(3);
}
// add the listener to the master set
FD_SET(listener, &master);
// keep track of the biggest file descriptor
fdmax = listener; // so far, it's this one
// main loop
for(;;) {
read_fds = master; // copy it
if (select(fdmax+1, &read_fds, NULL, NULL, NULL) == -1) {
perror("select");
exit(4);
}
// run through the existing connections looking for data to read
for(i = 0; i <= fdmax; i++) {
if (FD_ISSET(i, &read_fds)) { // we got one!!
if (i == listener) {
// handle new connections
addrlen = sizeof remoteaddr;
newfd = accept(listener,
(struct sockaddr *)&remoteaddr,
&addrlen);
if (newfd == -1) {
perror("accept");
}
else {
FD_SET(newfd, &master); // add to master set
if (newfd > fdmax) { // keep track of the max
fdmax = newfd;
}
std::cout << "selectserver: new connection on socket " << newfd;
/*
printf("selectserver: new connection from %s on "
"socket %d\n",
inet_ntop(remoteaddr.ss_family,get_in_addr((struct sockaddr*)&remoteaddr),remoteIP, INET6_ADDRSTRLEN),newfd);
*/
}
}
else {
// handle data from a client
if ((nbytes = recv(i, buf, sizeof buf, 0)) <= 0) {
// got error or connection closed by client
if (nbytes == 0) {
// connection closed
std::cout << "selectserver: socket " << i << " hung up";
}
else {
perror("recv");
}
close(i); // bye!
FD_CLR(i, &master); // remove from master set
}
else {
// we got some data from a client
for(j = 0; j <= fdmax; j++) {
// send to everyone!
if (FD_ISSET(j, &master)) {
// except the listener and ourselves
if (j != listener && j != i) {
if (send(j, buf, nbytes, 0) == -1) {
perror("send");
}
}
}
}
}
} // END handle data from client
} // END got new incoming connection
} // END looping through file descriptors
} // END for(;;)--and you thought it would never end!
return 0;
}
答案 0 :(得分：3)
getaddrinfo()可以返回多个IP地址。您正在循环遍历所有返回的地址，但是您在第一次成功bind()之后断开循环，然后在该单个套接字上调用listen()，而不管其套接字系列如何。由于您在调用AF_UNSPEC时使用的是getaddrinfo()，因此可能会为IPv4 AND {{1}返回 BOTH INADDR_ANY对于IPv6。
更改您的代码以侦听IN6ADDR_ANY_INIT返回的每个IP地址，并跟踪这些套接字，以便您可以在getaddrinfo()循环中使用所有这些套接字。如果你只是想听select()或INADDR_ANY，那么根本不可能使用IN6ADDR_ANY_INIT，因为你可以对getaddrinfo() / {进行硬编码{1}}调用这两个地址并完全摆脱循环。以这种方式使用socket()的目的是让它根据您提供的bind()提示决定您应该听什么。不要对其输出做出假设。
您也无法在Windows上使用getaddrinfo()，因此您需要重新编写AI_PASSIVE循环。 Windows上的套接字不使用文件描述符，因此您无法在调用fdmax时从select()循环，并且也会忽略0 <= fdmax的第一个参数。我建议不要在主FD_ISSET()中存储您的活动套接字描述符/句柄。请改用select()或其他合适的容器，然后在需要致电fd_set时动态创建新的std::list。这将在不同平台上更加便携。
尝试更像这样的事情：
fd_set如果您在支持双栈套接字的系统（如Windows）上运行代码，则可以将select()更改为#include <unistd.h>
#include <sys/types.h>
#ifdef __linux__
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#define SOCKET int
#define SOCKET_ERROR -1
#define INVALID_SOCKET -1
inline int closesocket(int s) { return close(s); }
inline int getLastSocketError() { return errno; }
#endif
#ifdef _WIN32
#include <winsock2.h>
#include <ws2tcpip.h>
inline int getLastSocketError() { return WSAGetLastError(); }
#endif
#include <iostream>
#include <list>
#include <algorithm>
#include <utility>
#define PORT "9034" // port we're listening on
#ifdef _WIN32
#define SELECT_MAXFD 0
#else
#define SELECT_MAXFD fdmax+1
#endif
enum eSocketType { stListener, stClient };
struct SocketInfo
{
SOCKET sckt;
eSocketType type;
};
SocketInfo makeSocketInfo(SOCKET sckt, eSocketType type) {
SocketInfo info;
info.sckt = sckt;
info.type = type;
return info;
}
// get sockaddr, IPv4 or IPv6:
void* get_in_addr(struct sockaddr *sa)
{
if (sa->sa_family == AF_INET) {
return &(((struct sockaddr_in*)sa)->sin_addr);
}
return &(((struct sockaddr_in6*)sa)->sin6_addr);
}
int main(void)
{
std::list<SocketInfo> master; // socket descriptors
std::list<SocketInfo>::iterator i, j;
SOCKET sckt, newsckt; // socket descriptors
fd_set read_fds; // temp file descriptor list for select()
#ifndef _WIN32
int fdmax; // maximum file descriptor number
#endif
struct sockaddr_storage remoteaddr; // client address
socklen_t addrlen;
char buf[256]; // buffer for client data
int nbytes;
char ipAddr[INET6_ADDRSTRLEN];
int yes = 1; // for setsockopt() SO_REUSEADDR, below
int rv;
struct addrinfo hints, *ai, *p;
#ifdef _WIN32
WSADATA wsaData; // Initialize Winsock
rv = WSAStartup(MAKEWORD(2,2), &wsaData);
if (NO_ERROR != rv) {
std::cerr << "WSA startup failed, error: " << rv << std::endl;
return 1;
}
#endif
// get us the listening sockets and bind them
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
hints.ai_flags = AI_PASSIVE;
rv = getaddrinfo(NULL, PORT, &hints, &ai);
if (rv != 0) {
std::cerr << "selectserver: getaddrinfo failed, error: " << gai_strerror(rv) << std::endl;
return 2;
}
for(p = ai; p != NULL; p = p->ai_next) {
sckt = socket(p->ai_family, p->ai_socktype, p->ai_protocol);
if (INVALID_SOCKET == sckt) {
std::cerr << "selectserver: socket failed, error: " << getLastSocketError() << std::endl;
continue;
}
// lose the pesky "address already in use" error message
setsockopt(sckt, SOL_SOCKET, SO_REUSEADDR, (const char *)&yes, sizeof(int));
//setsockopt(sckt, SOL_SOCKET, SO_REUSEADDR, "1", sizeof(int));
if (bind(sckt, p->ai_addr, p->ai_addrlen) < 0) {
std::cerr << "selectserver: bind failed, error: " << getLastSocketError() << std::endl;
closesocket(sckt);
continue;
}
// listen
if (listen(sckt, 10) < 0) {
std::cerr << "selectserver: listen failed, error: " << getLastSocketError() << std::endl;
closesocket(sckt);
continue;
}
/*
std::cout << "selectserver: listening on IP " << inet_ntop(p->ai_family, get_in_addr(p->ai_addr), ipAddr, sizeof(ipAddr)) << ", socket " << sckt << std::endl,
*/
// add the listener to the master list
master.push_back(makeSocketInfo(sckt, stListener));
}
freeaddrinfo(ai); // all done with this
// if we got here, it means we didn't get bound
if (master.empty()) {
std::cerr << "selectserver: failed to bind" << std::endl;
return 3;
}
// main loop
while (1) {
#ifndef _WIN32
fdmax = 0;
#endif
FD_ZERO(&read_fds);
for (i = master.begin(); i != master.end(); ++i) {
sckt = i->sckt;
FD_SET(sckt, &read_fds);
#ifndef _WIN32
fdmax = std::max(fdmax, sckt);
#endif
}
if (select(SELECT_MAXFD, &read_fds, NULL, NULL, NULL) < 0) {
std::cerr << "select failed, error: " << getLastSocketError() << std::endl;
return 4;
}
// run through the existing connections looking for data to read
for(i = master.begin(); i != master.end(); ) {
sckt = i->sckt;
if (!FD_ISSET(sckt, &read_fds)) {
++i;
continue;
}
// we got one!!
if (stListener == i->type) {
// handle a new connection
addrlen = sizeof(remoteaddr);
newsckt = accept(sckt, (struct sockaddr *)&remoteaddr, &addrlen);
if (INVALID_SOCKET == newsckt) {
std::cerr << "accept failed on socket " << sckt << ", error: " << getLastSocketError() << std::endl;
}
else {
master.push_back(makeSocketInfo(newsckt, stClient)); // add to master list
std::cout << "selectserver: new connection, socket " << newsckt << std::endl;
/*
std::cout << "selectserver: new connection from " << inet_ntop(remoteaddr.ss_family, get_in_addr((struct sockaddr*)&remoteaddr), ipAddr, sizeof(ipAddr)) << ", socket " << newsckt << std::endl,
*/
}
}
else {
// handle data from a client
nbytes = recv(sckt, buf, sizeof(buf), 0);
if (nbytes <= 0) {
// got error or connection closed by client
if (nbytes == 0) {
// connection closed
std::cout << "selectserver: socket " << sckt << " disconnected" << std::endl;
}
else {
std::cerr << "selectserver: recv failed on socket " << sckt << ", error: " << getLastSocketError() << std::endl;
}
closesocket(sckt); // bye!
i = master.erase(i); // remove from master list
continue;
}
// send to everyone!
// except a listener and ourselves
for(j = master.begin(); j != master.end(); ) {
if ((j->sckt != sckt) && (stClient == j->type)) {
if (send(j->sckt, buf, nbytes, 0) < 0) {
std::cerr << "selectserver: send failed on socket " << j->sckt << ", error: " << getLastSocketError() << std::endl;
closesocket(j->sckt); // bye!
j = master.erase(j); // remove from master list
continue;
}
}
++j;
}
}
++i;
}
}
for(i = master.begin(); i != master.end(); ++i) {
closesocket(i->sckt);
}
#ifdef _WIN32
WSACleanup();
#endif
return 0;
}
（或者只需硬编码AF_UNSPEC / { {1}}不使用AF_INET6）在socket()上仅创建IPv6侦听器，然后在其上禁用bind()套接字选项。这将允许IPv6侦听套接字接受IPv4和IPv6客户端，从而减少您需要创建的侦听套接字的数量。