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mcping.c
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mcping.c
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#include <sys/types.h>
#ifdef _WIN32
#include <Winsock2.h>
#include <Ws2tcpip.h>
#else
#include <sys/socket.h>
#include <fcntl.h>
#include <netdb.h>
#include <unistd.h>
#endif
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#define HANDSHAKE_SIZE 1024
#define STRING_BUF_SIZE 4096
#define PROTOCOL_VERSION 210
#define TIMEOUT_USEC 500000 // 500ms
#ifdef _WIN32
#pragma comment(lib, "Ws2_32.lib")
typedef SSIZE_T ssize_t;
#endif
int connect_w_to(struct addrinfo *addr, suseconds_t usec) {
int res;
long arg;
fd_set myset;
struct timeval tv;
int valopt;
socklen_t lon;
int soc;
// Create socket
soc = socket(addr->ai_family, addr->ai_socktype, addr->ai_protocol);
if (soc < 0) {
fprintf(stderr, "Error creating socket (%d %s)\n", errno, strerror(errno));
return -1;
}
// Set non-blocking
if ((arg = fcntl(soc, F_GETFL, NULL)) < 0) {
fprintf(stderr, "Error fcntl(..., F_GETFL) (%s)\n", strerror(errno));
return -1;
}
arg |= O_NONBLOCK;
if (fcntl(soc, F_SETFL, arg) < 0) {
fprintf(stderr, "Error fcntl(..., F_SETFL) (%s)\n", strerror(errno));
return -1;
}
// Trying to connect with timeout
res = connect(soc, addr->ai_addr, addr->ai_addrlen);
if (res < 0) {
if (errno == EINPROGRESS) {
do {
tv.tv_sec = 0;
tv.tv_usec = usec;
FD_ZERO(&myset);
FD_SET(soc, &myset);
res = select(soc+1, NULL, &myset, NULL, &tv);
if (res < 0 && errno != EINTR) {
fprintf(stderr, "Error connecting %d - %s\n", errno, strerror(errno));
return -1;
}
else if (res > 0) {
// Socket selected for write
lon = sizeof(int);
if (getsockopt(soc, SOL_SOCKET, SO_ERROR, (void*)(&valopt), &lon) < 0) {
fprintf(stderr, "Error in getsockopt() %d - %s\n", errno, strerror(errno));
return -1;
}
// Check the value returned...
if (valopt) {
return -1;
}
break;
}
else {
return -1;
}
} while (1);
}
else {
fprintf(stderr, "Error connecting %d - %s\n", errno, strerror(errno));
return -1;
}
}
// Set to blocking mode again...
if( (arg = fcntl(soc, F_GETFL, NULL)) < 0) {
fprintf(stderr, "Error fcntl(..., F_GETFL) (%s)\n", strerror(errno));
return -1;
}
arg &= (~O_NONBLOCK);
if( fcntl(soc, F_SETFL, arg) < 0) {
fprintf(stderr, "Error fcntl(..., F_SETFL) (%s)\n", strerror(errno));
return -1;
}
return soc;
}
int set_timeout(int sfd, suseconds_t usec) {
struct timeval timeout;
timeout.tv_sec = 0;
timeout.tv_usec = usec;
if (setsockopt (sfd, SOL_SOCKET, SO_RCVTIMEO, (char *)&timeout, sizeof(timeout)) < 0) {
fprintf(stderr, "setsockopt failed\n");
return -1;
}
if (setsockopt (sfd, SOL_SOCKET, SO_SNDTIMEO, (char *)&timeout, sizeof(timeout)) < 0) {
fprintf(stderr, "setsockopt failed\n");
return -1;
}
return 0;
}
size_t build_handshake(unsigned char *buffer, char *host, unsigned short port) {
size_t host_len = strlen(host);
size_t len = 1 /* packet id */ + 2 /* Protocol version */;
len += 1 /* str len */ + host_len;
len += 2; // port
len += 1; // state
size_t i = 0;
buffer[i++] = len;
buffer[i++] = 0; /* packet id */
buffer[i++] = PROTOCOL_VERSION;
buffer[i++] = 1; /* encoded protocol version - varint */
buffer[i++] = host_len;
memcpy(buffer + i, host, host_len);
i += host_len;
buffer[i++] = (port >> 8) & 0xFF; /* port little-endian */
buffer[i++] = port & 0xFF;
buffer[i] = 1; // next state
return len + 1; /* add length byte */
}
ssize_t read_byte(const int sfd, void *buf) {
ssize_t nread;
nread = recv(sfd, buf, 1, 0);
if (nread == -1) {
perror("Read byte");
exit(EXIT_FAILURE);
}
return nread;
}
int read_varint(const int sfd) {
int numread = 0;
int result = 0;
int value;
char byte;
do {
if (read_byte(sfd, &byte) == 0){
fprintf(stderr, "Failed read varint: eof\n");
exit(EXIT_FAILURE);
}
value = byte & 0x7F;
result |= value << (7 * numread);
numread++;
if (numread > 5) {
fprintf(stderr, "Error reading varint: varint too big\n");
exit(EXIT_FAILURE);
}
} while ((byte & 0x80) != 0);
return result;
}
int main(int argc, char **argv) {
unsigned short port;
char port_str[6];
struct addrinfo hints;
struct addrinfo *result, *rp;
int sfd, s, json_len;
size_t len;
ssize_t nread;
char byte;
unsigned char handshake[HANDSHAKE_SIZE];
char request[] = {0x1, 0x0};
char string[STRING_BUF_SIZE];
if (argc < 2) {
printf("MC Ping 1.2.0, Minecraft Server List Ping tool.\n");
printf("Usage: mcping <host> <port>\n");
return EXIT_FAILURE;
}
if (strlen(argv[1]) > 250) {
fprintf(stderr, "Hostname too long\n");
return EXIT_FAILURE;
}
if (argc < 3) {
port = 25565;
} else {
port = atoi(argv[2]);
}
if (port == 0) {
fprintf(stderr, "Invalid port\n");
return EXIT_FAILURE;
}
#ifdef _WIN32
WORD wVersionRequested;
WSADATA wsaData;
int err;
/* Use the MAKEWORD(lowbyte, highbyte) macro declared in Windef.h */
wVersionRequested = MAKEWORD(2, 2);
err = WSAStartup(wVersionRequested, &wsaData);
if (err != 0) {
/* Tell the user that we could not find a usable */
/* Winsock DLL. */
fprintf(stderr, "WSAStartup failed with error: %d\n", err);
return EXIT_FAILURE;
}
/* Confirm that the WinSock DLL supports 2.2.*/
/* Note that if the DLL supports versions greater */
/* than 2.2 in addition to 2.2, it will still return */
/* 2.2 in wVersion since that is the version we */
/* requested. */
if (LOBYTE(wsaData.wVersion) != 2 || HIBYTE(wsaData.wVersion) != 2) {
/* Tell the user that we could not find a usable */
/* WinSock DLL. */
fprintf(stderr, "Could not find a usable version of Winsock.dll\n");
WSACleanup();
return EXIT_FAILURE;
}
#endif
/* Obtain address(es) matching host/port */
memset(&hints, 0, sizeof(struct addrinfo));
hints.ai_family = AF_UNSPEC; /* Allow IPv4 or IPv6 */
hints.ai_socktype = SOCK_STREAM; /* TCP socket */
hints.ai_flags = 0;
hints.ai_protocol = 0; /* Any protocol */
sprintf(port_str, "%d", port);
s = getaddrinfo(argv[1], port_str, &hints, &result);
if (s != 0) {
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(s));
return EXIT_FAILURE;
}
/* getaddrinfo() returns a list of address structures.
Try each address until we successfully connect(2).
If socket(2) (or connect(2)) fails, we (close the socket
and) try the next address. */
for (rp = result; rp != NULL; rp = rp->ai_next) {
sfd = connect_w_to(rp, TIMEOUT_USEC);
if (sfd != -1) {
break;
}
close(sfd);
}
if (rp == NULL) { /* No address succeeded */
fprintf(stderr, "Could not connect\n");
return EXIT_FAILURE;
}
if (set_timeout(sfd, TIMEOUT_USEC) == -1) {
return EXIT_FAILURE;
}
freeaddrinfo(result);
len = build_handshake(handshake, argv[1], port);
if (send(sfd, handshake, len, 0) != len) {
fprintf(stderr, "Failed to send handshake\n");
return EXIT_FAILURE;
}
if (send(sfd, request, 2, 0) != 2) {
fprintf(stderr, "Failed to send request\n");
return EXIT_FAILURE;
}
read_varint(sfd); /* read packet length */
if (read_byte(sfd, &byte) == 0) { /* read packet id */
fprintf(stderr, "Failed to read\n");
return EXIT_FAILURE;
}
if (byte != 0) {
fprintf(stderr, "Unknown packet id\n");
return EXIT_FAILURE;
}
/* read json and print to stdout */
json_len = read_varint(sfd);
while(json_len > 0) {
nread = recv(sfd, string, STRING_BUF_SIZE, 0);
if (nread == -1) {
perror("json read");
return EXIT_FAILURE;
}
json_len -= nread;
fwrite(string, 1, nread, stdout);
}
return EXIT_SUCCESS;
}