My client program needs to send a large file to the server program. After the client connects to the server and the server accepts it, the clients specifies the name of the file which it would be sending. Now, the client needs to send the file using TCP.
I know that if the size of the file is small (less than 1k bytes?), I can send it directly using a single call to the "send" function in socket programming. However, does the same work if my file size is large, say about 100 MB? I want to know does "send" by itself handle the task of breaking the large data into packets and sending them reliably or should I be the one handling this?
Thanks.
I am trying something similar & My client code looks like this
static void send_file(char *ipAddress, char *filename)
{
struct sockaddr_in serverAddr;
int skt;
uint32_t addr_size;
uint32_t sz;
int32_t sent_bytes;
FILE *fp;
if ( inet_pton(AF_INET, ipAddress, &(serverAddr.sin_addr)) ){
skt = socket(PF_INET, SOCK_STREAM, 0);
serverAddr.sin_family = AF_INET;
}
else {
inet_pton(AF_INET6, ipAddress, &(serverAddr.sin_addr));
skt = socket(PF_INET6, SOCK_STREAM, 0);
serverAddr.sin_family = AF_INET6;
}
serverAddr.sin_port = htons(7891);
memset(serverAddr.sin_zero, '\0', sizeof(serverAddr.sin_zero));
addr_size = sizeof(serverAddr);
connect(skt, (struct sockaddr *) &serverAddr, addr_size);
/*find file size*/
fp = fopen(filename, "r");
fseek(fp,0,SEEK_END);
sz = ftell(fp);
rewind(fp);
sent_bytes = send(skt, fp, sz, 0);
printf("sent %d bytes\n", sent_bytes);
fclose(fp);
}
Related
I'm trying to connect to a remote peer (which I don't have directory access other than connecting to it via socket and ping) via SCTP. Assuming that I have connected succesfully, what should be the value of my sctp_status.sstate if I try calling getsocktopt()? Mine is SCTP_COOKIE_ECHOED(3) according to sctp.h. Is it correct? Shouldn't it be SCTP_ESTABLISHED?
Because I tried sending message to the remote peer with this code:
ret = sctp_sendmsg (connSock, (void *) data, (size_t) strlen (data), (struct sockaddr *) &servaddr, sizeof (servaddr), 46, 0, 0, 0, 0);
It returned the number of bytes I tried sending. Then when I tried catching if there's any response:
ret = sctp_recvmsg (connSock, (void *) reply, sizeof (reply), NULL,
NULL, NULL, &flags);
It returns -1 with errno of ECONNRESET(104). What are the possible mistakes in my code, or maybe in my flow? Did I miss something?
Thanks in advance for answering. Will gladly appreciate that. :)
Update: Here down below is my client code in connecting to the remote peer. It's actually a node addon for me to use since SCTP is not fully supported in node. Using lksctp-tools package to include the headers.
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <netinet/sctp.h>
#include <arpa/inet.h>
#include <signal.h>
#define MAX_BUFFER 1024
int connSock = 0;
int connect(char host[], int port, char remote_host[], int remote_port, int timeout) {
int ret, flags;
fd_set rset, wset;
struct sockaddr_in servaddr;
struct sockaddr_in locaddr;
struct sctp_initmsg initmsg;
struct timeval tval;
struct sctp_status status;
socklen_t opt_len;
errno = 0;
connSock = socket (AF_INET, SOCK_STREAM, IPPROTO_SCTP);
flags = fcntl(connSock, F_GETFL, 0);
fcntl(connSock, F_SETFL, flags | O_NONBLOCK);
if (connSock == -1)
{
return (-1);
}
memset(&locaddr, 0, sizeof(locaddr));
locaddr.sin_family = AF_INET;
locaddr.sin_port = htons(port);
locaddr.sin_addr.s_addr = inet_addr(host);
ret = bind(connSock, (struct sockaddr *)&locaddr, sizeof(locaddr));
if (ret == -1)
{
return (-1);
}
memset (&initmsg, 0, sizeof (initmsg));
initmsg.sinit_num_ostreams = 5;
initmsg.sinit_max_instreams = 5;
initmsg.sinit_max_attempts = 10;
ret = setsockopt(connSock, IPPROTO_SCTP, SCTP_INITMSG, &initmsg, sizeof(initmsg));
if (ret == -1)
{
return (-1);
}
memset (&servaddr, 0, sizeof (servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons (remote_port);
servaddr.sin_addr.s_addr = inet_addr (remote_host);
if((ret = connect (connSock, (struct sockaddr *) &servaddr, sizeof (servaddr))) < 0)
if (errno != EINPROGRESS)
return (-1);
if (ret == 0) {
fcntl(connSock, F_SETFL, flags);
return 0;
}
FD_ZERO(&rset);
FD_SET(connSock, &rset);
wset = rset;
tval.tv_sec = timeout;
tval.tv_usec = 0;
ret = select(connSock+1, &rset, &wset, NULL, timeout ? &tval : NULL);
if (ret == 0) {
close(connSock);
errno = ETIMEDOUT;
return(-1);
}
else if (ret < 0) {
return(-1);
}
fcntl(connSock, F_SETFL, flags);
opt_len = (socklen_t) sizeof(struct sctp_status);
getsockopt(connSock, IPPROTO_SCTP, SCTP_STATUS, &status, &opt_len);
printf ("assoc id = %d\n", status.sstat_assoc_id);
printf ("state = %d\n", status.sstat_state);
printf ("instrms = %d\n", status.sstat_instrms);
printf ("outstrms = %d\n", status.sstat_outstrms);
return 0;
}
int sendMessage(char remote_host[], int remote_port, char data[]) {
int ret, flags;
struct sockaddr_in servaddr;
char reply[1024];
errno = 0;
memset (&servaddr, 0, sizeof (servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons (remote_port);
servaddr.sin_addr.s_addr = inet_addr (remote_host);
printf("\nSending %s (%li bytes)", data, strlen(data));
ret = sctp_sendmsg (connSock, (void *) data, (size_t) strlen (data),
(struct sockaddr *) &servaddr, sizeof (servaddr), 46, 0, 0, 0, 0);
if (ret == -1)
{
printf("\nError sending errno(%d)", errno);
return -1;
}
else {
ret = sctp_recvmsg (connSock, (void *) reply, sizeof (reply), NULL,
NULL, NULL, &flags);
if (ret == -1)
{
printf("\nError receiving errno(%d)", errno);
return -1;
}
else {
printf("\nServer replied with %s", reply);
return 0;
}
}
}
int getSocket() {
return connSock;
}
I don't know if there's anything significant I need to set first before connecting that I missed out. I got the snippet from different sources so it's quite messy.
Another update, here's the tshark log of that code when executed:
3336.919408 local -> remote SCTP 82 INIT
3337.006690 remote -> local SCTP 810 INIT_ACK
3337.006727 local -> remote SCTP 774 COOKIE_ECHO
3337.085390 remote -> local SCTP 50 COOKIE_ACK
3337.086650 local -> remote SCTP 94 DATA
3337.087277 remote -> local SCTP 58 ABORT
3337.165266 remote -> local SCTP 50 ABORT
Detailed tshark log of this here.
Looks like the remote sent its COOKIE_ACK chunk but my client failed to set its state to ESTABLISHED (I double checked the sstate value of 3 here).
If the association setup processes completed the state should be SCTP_ESTABLISHED. SCTP_COOKIE_ECHOED indicated that association has not completely established. It means that originating side (your localhost in this case) has sent (once or several times) COOKIE_ECHO chunk which has not been acknowledged by COOKIE_ACK from remote end.
You can send messages in this state (SCTP will simply buffer it until it get COOKIE_ACK and resend it later on).
It is hard to say what went wrong based on information you provided. At this stage it is probably will be worth diving into wireshark trace, to see what remote side is replying on your COOKIE_ECHO.
Also if you can share your client/server side code that might help to identify the root cause.
UPDATE #1:
It should be also noted that application can abort association them self (e.g. if this association is not configured on that server). If you trying to connect to the random server (rather than your specific one) that is quite possible and actually makes sense in your case. In this case state of association on your side is COOKIE_ECHOED because COOKIE_ACK has not arrived yet (just a race condition). As I said previously SCTP happily accepts your data in this state and just buffers it until it receives COOKIE_ACK. SCTP on remote side sends COOKIE_ACK straight away, even before the application received execution control in accept(). If application decided to terminate the association in ungraceful way, it will send ABORT (that is your first ABORT in wireshark trace). Your side has not received this ABORT yet and sends DATA chunk. Since remote side considers this association as already terminated it cannot process DATA chunk, so it treats it as out of the blue (see RFC 4960 chapter 8.4) and sends another ABORT with t-bit set to 1.
I guess this is what happened in your case. You can confirm it easily just by looking into wireshark trace.
I am receiving multiple messages through a socket using:
result = recvmmsg(socket_, &messages_[0], MAX_NUM_MSG, MSG_WAITFORONE, NULL);
And I want get the source address and port, but I am getting an error in the struct assignment when I try:
msg = &messages_[0];
***struct sockaddr *src = &msg->msg_hdr.msg_name;***
srcport = ntohs(src->sin_port);
srcaddr = ntohl(src->sin_addr.s_addr);
invalid conversion from ‘void**’ to ‘sockaddr*'
The recvmmsg system call is an extension of recvmsg. As described in recvmsg: The msg_name field points to a caller-allocated buffer that is used to return the source address
That means you should preallocate memory space for msg_name by yourself, and also you should specify msg_namelen, please try:
sockaddr_in addrs[MAX_NUM_MSG];
for (int i = 0; i < MAX_NUM_MSG; ++i) {
messages_[i].msg_hdr.msg_name = &addrs[i];
messages_[i].msg_hdr.msg_namelen = sizeof(sockaddr_in);
}
So that you can access address when you have at least one message by doing (Remember to use sockaddr_in but not sockaddr):
struct sockaddr_in *src = messages_[0].msg_hdr.msg_name;
I'm trying to write a transparent proxy that translates arbitrary UDP packets to a custom protocol and back again. I'm trying to use transparent proxying to read the incoming UDP packets that need translation, and to write the outgoing UDP packets that have just been reverse-translated.
My setup for the socket I use for both flavors of UDP sockets is as follows:
static int
setup_clear_sock(uint16_t proxy_port)
{
struct sockaddr_in saddr;
int sock;
int val = 1;
socklen_t ttllen = sizeof(std_ttl);
sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
if (sock < 0)
{
perror("Failed to create clear proxy socket");
return -1;
}
if (getsockopt(sock, IPPROTO_IP, IP_TTL, &std_ttl, &ttllen) < 0)
{
perror("Failed to read IP TTL option on clear proxy socket");
return -1;
}
if (setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val)) < 0)
{
perror("Failed to set reuse address option on clear socket");
return -1;
}
if (setsockopt(sock, IPPROTO_IP, IP_TRANSPARENT, &val, sizeof(val)) < 0)
{
perror("Failed to set transparent proxy option on clear socket");
return -1;
}
saddr.sin_family = AF_INET;
saddr.sin_port = htons(proxy_port);
saddr.sin_addr.s_addr = INADDR_ANY;
if (bind(sock, (struct sockaddr *) &saddr, sizeof(saddr)) < 0)
{
perror("Failed to bind local address to clear proxy socket");
return -1;
}
return sock;
}
I have two distinct, but possibly related problems. First, when I read an incoming UDP packet from this socket, using this code:
struct sock_double_addr_in
{
__SOCKADDR_COMMON (sin_);
in_port_t sin_port_a;
struct in_addr sin_addr_a;
sa_family_t sin_family_b;
in_port_t sin_port_b;
struct in_addr sin_addr_b;
unsigned char sin_zero[sizeof(struct sockaddr) - __SOCKADDR_COMMON_SIZE - 8
- sizeof(struct in_addr) - sizeof(in_port_t)];
};
void
handle_clear_sock(void)
{
ssize_t rcvlen;
uint16_t nbo_udp_len, coded_len;
struct sockaddr_in saddr;
struct sock_double_addr_in sdaddr;
bch_coding_context_t ctx;
socklen_t addrlen = sizeof(sdaddr);
rcvlen = recvfrom(sock_clear, &clear_buf, sizeof(clear_buf),
MSG_DONTWAIT | MSG_PROXY,
(struct sockaddr *) &sdaddr, &addrlen);
if (rcvlen < 0)
{
perror("Failed to receive a packet from clear socket");
return;
}
....
I don't see a destination address come back in sdaddr. The sin_family_b, sin_addr_b, and sin_port_b fields are all zero. I've done a block memory dump of the structure in gdb, and indeed the bytes are coming back zero from the kernel (it's not a bad placement of the field in my structure definition).
Temporarily working around this by hard-coding a fixed IP address and port for testing purposes, I can debug the rest of my proxy application until I get to the point of sending an outgoing UDP packet that has just been reverse-translated. That happens with this code:
....
udp_len = ntohs(clear_buf.u16[2]);
if (udp_len + 6 > decoded_len)
fprintf(stderr, "Decoded fewer bytes (%u) than outputting in clear "
"(6 + %u)!\n", decoded_len, udp_len);
sdaddr.sin_family = AF_INET;
sdaddr.sin_port_a = clear_buf.u16[0];
sdaddr.sin_addr_a.s_addr = coded_buf.u32[4];
sdaddr.sin_family_b = AF_INET;
sdaddr.sin_port_b = clear_buf.u16[1];
sdaddr.sin_addr_b.s_addr = coded_buf.u32[3];
if (sendto(sock_clear, &(clear_buf.u16[3]), udp_len, MSG_PROXY,
(struct sockaddr *) &sdaddr, sizeof(sdaddr)) < 0)
perror("Failed to send a packet on clear socket");
}
and the packet never shows up. I've checked the entire contents of the sdaddr structure I've built, and all fields look good. The UDP payload data looks good. There's no error coming back from the sendto() syscall -- indeed, it returns zero. And the packet never shows up in wireshark.
So what's going on with my transparent proxying? How do I get this to work? (FWIW: development host is a generic x86_64 ubuntu 14.04 LTS box.) Thanks!
Alright, so I've got half an answer.
It turns out if I just use a RAW IP socket, with the IP_HDRINCL option turned on, and build the outgoing UDP packet in userspace with a full IP header, the kernel will honor the non-local source address and send the packet that way.
I'm now using a third socket, sock_output, for that purpose, and decoded UDP packets are coming out correctly. (Interesting side note: the UDP checksum field must either be zero, or the correct checksum value. Anything else causes the kernel to silently drop the packet, and you'll never see it go out. The kernel won't fill in the proper checksum for you if you zero it out, but if you specify it, it will verify that it's correct. No sending UDP with intentionally bad checksums this way.)
So the first half of the question remains: when I read a packet from sock_clear with the MSG_PROXY flag to recvfrom(), why do I not get the actual destination address in the second half of sdaddr?
I'm writing a game wich playing on LAN with socket. I use 4 bytes length prefix to know how many data in the rest like this:
void trust_recv(int sock, int length, char *buffer)
{
int recved = 0;
int justRecv;
while(recved < length) {
justRecv = recv(sock, buffer + recved, length - recved, 0);
if (justRecv < 0) return;
recved += justRecv;
}
}
void onDataArrival(int sock)
{
int length;
char *data;
trust_recv(sock, 4, (char *) &length);
data = new char[length];
trust_recv(sock, length, data);
do_somethings_with_data(data);
}
The problem is if someone (an intruder or hacker for example) sends data with other format (maybe only 2 bytes or the length of the rest lower than 4 bytes prefix value) or an network problem, my application will be go to "not responding" state and have to close (because I use blocking socket). How to make my socket application more flexible but don't swith socket to non-blocking mode to pass this issue? (Or any ideas for organize data or algorithms as well)
You can set a receive timeout, during the socket setup phase, with setsockopt() call and SO_RCVTIMEO parameter;
struct timeval tv;
tv.tv_sec =8;
tv.tv_usec = 0 ;
if (setsockopt (your_sock_fd, SOL_SOCKET, SO_RCVTIMEO, (char *)&tv, sizeof tv)
perror(“setsockopt error”);
then test the return of recv() and his errno
if (justRecv < 0)
{
if (errno == EAGAIN)
perror("TIMEOUT!");
return;
}
I want make ping with timeout and TTL. I use code by Apple ("Simple Ping"). I read it
"iOS ping with timeout". I change code:
CFSocketNativeHandle sock = CFSocketGetNative(self->_socket);
struct timeval tv;
tv.tv_sec = 0;
tv.tv_usec = 100000; // 0.1 sec
setsockopt(sock, SOL_SOCKET, SO_SNDTIMEO, (void *)&tv, sizeof(tv));
bytesSent = sendto(
sock,
[packet bytes],
[packet length],
0,
(struct sockaddr *) [self.hostAddress bytes],
(socklen_t) [self.hostAddress length]
);
But I don't understand where I should put code that will show me timeout of receiving packets. Also I need to make ping with TTL (time-to-live) information. I want get information based on this pattern: icmp_seq=count from=ip_address ttl=value_of_ttl time=value_of_replytime_ms
To modify the default TTL in the IP Header, call setsockopt with IP_TTL as parameter (tested with IPv4):
- (BOOL)setTTL:(int)ttl{
CFSocketNativeHandle sock = CFSocketGetNative(self->_socket);
int status = setsockopt(sock, IPPROTO_IP, IP_TTL, &ttl, sizeof(ttl));
if(status < 0)
{
return NO;
}
return YES;
}
The "iOS ping with timeout" example add a output timeout to the socket. From what I understand, it will timeout if the packet is not been sent by the socket within this period. I could be wrong, but I cannot find this "timeout" value from the ICMP header and IPv4 header (ICMP Packet format).
Here are the console log and request, response packet captured using apple's simple ping:
If you only want to know the response time of the ping, I guess you can track it yourself in the delegate methods. Get timestamps when "didSendPacket" and "didReceivePingResponsePacket" functions called and then compare the difference.
You can always put some limit time on the receivefrom:
tv.tv_sec = 0;
tv.tv_usec = 10000;
setsockopt(recv_sock, SOL_SOCKET, SO_RCVTIMEO, (char *)&tv,sizeof(struct timeval));