[Just 2 minor questions on the ground of this remaining]
I try to write a simple server/client in C to send messages over sockets. It must run under Linux and Windows with MinGW. I found many examples for Linux but way to many arent working with Windows. It would be really nice if you would help me.
For the server I have something I dont understand.
What I’m doing on server-side?
- Need to initialise WSA on Windows, nothing on Linux.
- Create a socket for the server on server-side.
- Create struct sockaddr_in for the server.
- Bind the socket on ANY-IP.
- Listen on the socket.
- Accept connections, handle connection with the newSocket.
- Close the new Socket repeat with 6).
It is only working correctly if I dont close the newSocket, but why? (EBADF error)
Code Update after Edit2:
// IMPORTANT: On linker errors try -lws2_32 as Linkerparameter #ifdef __WIN32__ # include <winsock2.h> // used for sockets with windows, needs startup / shutdown # include <ws2tcpip.h> // for MinGW / socklen_t # define INIT_SOCKET_SYSTEM WSADATA wsaData;if (WSAStartup(MAKEWORD(2,2), &wsaData) != 0) {printf ("Error initialising WSA.n");exit(6);} # define CLEAR_SOCKET_SYSTEM WSACleanup(); # include <windows.h> // for Sleep # define SLEEP Sleep(10); // sleeping 10ms # define CLOSE_SOCKET_FUNCTION closesocket #else # include <sys/socket.h> # define INIT_SOCKET_SYSTEM printf("Linux dont need a special init for sockets, so all fine.n"); # define CLEAR_SOCKET_SYSTEM printf("Linux dont need a special clear for sockets, so all fine.n"); # include <time.h> # define SLEEP sleep(1); // sleeping a second :-/ # define CLOSE_SOCKET_FUNCTION close #endif #include <stdio.h> #include <sys/stat.h> #include <stdbool.h> #include <strings.h> // used for bzero //used in the tutorial but not necessary!? //#include <sys/types.h> //#include <unistd.h> //#include <stdlib.h> /* could be still useful // polling 10ms... //#include <time.h> //#define SLEEP time_t tStart, tEnd;time(&tStart);do {time(&tEnd);} while (difftime(tEnd, tStart) < 0.01); */ /* Random Sources * http://pubs.opengroup.org/onlinepubs/9699919799/ * http://linux.die.net/man/2 * http://stackoverflow.com/questions/31765278/simple-webserver-wont-work * http://blog.stephencleary.com/2009/05/using-socket-as-server-listening-socket.html * * http://cs.baylor.edu/~donahoo/practical/CSockets/WindowsSockets.pdf */ // functions void createListenSocket(int * retListenSocket, const int port, bool * isRunning); void listenFor(int * listenSocket, bool * isRunning); void acceptFor(int * listenSocket, socklen_t * addrlen, bool * isRunning); void handleConnection(int * inSocket, struct sockaddr_in * addClient); // http://www.gnu.org/software/libc/manual/html_node/Cleanups-on-Exit.html int * cleanSocket; void cleanUp() { CLOSE_SOCKET_FUNCTION(* cleanSocket); CLEAR_SOCKET_SYSTEM } //[todo] WSAGetLastError handling for windows int main(int argc, char ** argv) { atexit(cleanUp); bool isRunning = true; socklen_t addressLen = sizeof(struct sockaddr_in); // create listening socket const int port = 15000; int listenSocket; cleanSocket = &listenSocket; createListenSocket(&listenSocket, port, &isRunning); listenFor(&listenSocket, &isRunning); while (isRunning) { acceptFor(&listenSocket, &addressLen, &isRunning); SLEEP } return 0; } void createListenSocket(int * retListenSocket, const int port, bool * isRunning) { INIT_SOCKET_SYSTEM struct sockaddr_in addServer; (* retListenSocket) = socket(AF_INET, SOCK_STREAM, 0); int tErr = errno; if ((* retListenSocket) > 0) { printf("The socket was created (%i)n", * retListenSocket); } else { printf("Couldnt create socketn- "); switch (tErr) { case EACCES: printf("Permission to create a socket of the specified type and/or protocol is denied.n"); break; case EAFNOSUPPORT: printf("The implementation does not support the specified addServer family.n"); break; case EINVAL: printf("Unknown protocol, or protocol family not available. OR Invalid flags in type.n"); break; case EMFILE: printf("Process file table overflow.n"); break; case ENFILE: printf("The system limit on the total number of open files has been reached.n"); break; case ENOBUFS: printf("Insufficient memory is available. The socket cannot be created until sufficient resources are freed.n"); break; case ENOMEM: printf("Insufficient memory is available. The socket cannot be created until sufficient resources are freed.n"); break; case EPROTONOSUPPORT: printf("The protocol type or the specified protocol is not supported within this domain.n"); break; default: printf("unspecified error %i ... n", tErr); break; } * isRunning = false; return; } addServer.sin_family = AF_INET; addServer.sin_addr.s_addr = INADDR_ANY; addServer.sin_port = htons(port); if (bind(* retListenSocket, (struct sockaddr * ) &addServer, sizeof(struct sockaddr_in)) == 0) { printf("Socket bind successfulln"); } else { printf("Socket bind failedn"); * isRunning = false; return; } } // http://linux.die.net/man/2/listen / http://pubs.opengroup.org/onlinepubs/9699919799/ void listenFor(int * listenSocket, bool * isRunning) { int t = listen(* listenSocket, 10); int tErr = errno; if (t < 0) { printf("Error while listeningn- "); //perror("server: listen"); switch (tErr) { case EADDRINUSE: printf("Another socket is already listening on the same port.n"); break; case EBADF: printf("The argument sockfd is not a valid descriptor.n"); break; case ENOTSOCK: printf("The argument sockfd is not a socketn"); break; case EOPNOTSUPP: printf("The socket is not of a type that supports the listen() operationn"); break; default: printf("Undefined Error%in", tErr); break; } * isRunning = false; } } // http://linux.die.net/man/2/accept / http://pubs.opengroup.org/onlinepubs/9699919799/ void acceptFor(int * listenSocket, socklen_t * addrlen, bool * isRunning) { struct sockaddr_in addClient; memset(&addClient, 0, sizeof(addClient)); int NewSocket = accept(* listenSocket, (struct sockaddr *) &addClient, addrlen); int tErr = errno; //write(NewSocket, "Hoin", 4); if (tErr != 0) { printf("Error while acceptingn- "); switch (tErr) { case EAGAIN: printf("The socket is marked nonblocking and no connections are present to be accepted. POSIX.1-2001 allows either error to be returned for this case, and does not require these constants to have the same value, so a portable application should check for both possibilities.n"); break; case EWOULDBLOCK: printf("The socket is marked nonblocking and no connections are present to be accepted. POSIX.1-2001 allows either error to be returned for this case, and does not require these constants to have the same value, so a portable application should check for both possibilities.n"); break; case EBADF: printf("The descriptor is invalidn"); break; case ECONNABORTED: printf("A connection has been aborted.n"); break; case EFAULT: printf("The addr argument is not in a writable part of the user addServer space.n"); break; case EINTR: printf("The system call was interrupted by a signal that was caught before a valid connection arrived; see signal(7).n"); break; case EINVAL: printf("Socket is not listening for connections, or addrlen is invalid (e.g., is negative). or (accept4()) invalid value in flagsn"); break; case EMFILE: printf("The per-process limit of open file descriptors has been reached.n"); break; case ENFILE: printf("The system limit on the total number of open files has been reached.n"); break; case ENOBUFS: printf("Not enough free memory. This often means that the memory allocation is limited by the socket buffer limits, not by the system memory.n"); break; case ENOMEM: printf("Not enough free memory. This often means that the memory allocation is limited by the socket buffer limits, not by the system memory.n"); break; case ENOTSOCK: printf("The descriptor references a file, not a socket.n"); break; case EOPNOTSUPP: printf("The referenced socket is not of type SOCK_STREAM.n"); break; case EPROTO: printf("Protocol errorn"); break; default: printf("Undefined Error %in", tErr); break; } * isRunning = false; } else if (NewSocket != -1) { handleConnection(&NewSocket, &addClient); } } void handleConnection(int * inSocket, struct sockaddr_in * addClient) { if (* inSocket > 0){ int bufferSize = 1024; char * buffer = malloc(bufferSize); memset(buffer, '', bufferSize); char response[] = "HTTP/1.1 200 OKrn" "Content-Type: text/htmlrnrn" "<html><head><title>test</title>" "<html><body><H1>Hello world</H1></body></html>"; printf("The Client is connected from %s ...n", inet_ntoa((* addClient).sin_addr)); //[todo] handle full buffer int received = recv(* inSocket, buffer, bufferSize, 0); printf("%snbuffer size: %in", buffer, bufferSize); send(* inSocket, response, strlen(response), 0); printf("=> response sendn"); CLOSE_SOCKET_FUNCTION(* inSocket); } }
What I’m doing on client-side?
- Need to initialise WSA on Windows, nothing on Linux.
- Create a socket for the client on client-side.
- Create struct sockaddr_in for the server.
[try 1]
- Create struct sockaddr_in for the client.
- Bind the socket to the struct for client.
- Connect with client Socket to server-struct.
- Send a message.
[try 2]
- Use sendto because I only want to send one message.
Both isnt working, I think my problem is the struct sockaddr_in, but I havent any idea right know why. What I’m doing wrong here?
View Edit 3 for solutions.
#ifdef __WIN32__ # include <winsock2.h> // used for sockets with windows, needs startup / shutdown # include <ws2tcpip.h> // for MinGW / socklen_t / InetPtonA # define INIT_SOCKET_SYSTEM WSADATA wsaData;if (WSAStartup(MAKEWORD(2,2), &wsaData) != 0) {printf ("Error initialising WSA.n");exit(6);} # define CLEAR_SOCKET_SYSTEM WSACleanup(); # include <windows.h> // for Sleep # define SLEEP Sleep(10); // sleeping 10ms #else # include <sys/socket.h> # define INIT_SOCKET_SYSTEM printf("Linux dont need a special init for sockets, so all fine.n"); # define CLEAR_SOCKET_SYSTEM printf("Linux dont need a special clear for sockets, so all fine.n"); # include <time.h> # define SLEEP sleep(1); // sleeping a second :-/ #endif #include <stdio.h> #include <sys/stat.h> #include <stdbool.h> // Step 1, create lokal Access point void createSocket(int * mySocket); // Step 2, create the target address struct sockaddr_in getTargetAddress(char * ip, int port); int * cleanSocket; void cleanUp() { close(* cleanSocket); CLEAR_SOCKET_SYSTEM } int main() { int mySocket; // Step 1 create you Socket createSocket(&mySocket); // Step 2 get target struct sockaddr_in serverAddress = getTargetAddress("127.0.0.1", 15000); //struct sockaddr_in myAddress = getTargetAddress("127.0.0.1", 15000); // Step 3 bind & connect or sendto //bind(mySocket, (const struct sockaddr *) &myAddress, sizeof(myAddress)); //connect(mySocket, (const struct sockaddr * )&serverAddress, sizeof(serverAddress)); char * question = "Whats up?n"; printf("sending %sn", question); //send(mySocket, question, strlen(question), 0); // try to use protocol? sendto(mySocket, question, strlen(question), 0, (const struct sockaddr *) &serverAddress, sizeof(serverAddress)); printf("sended!n"); close(mySocket); return 0; } void createSocket(int * mySocket) { INIT_SOCKET_SYSTEM if ((* mySocket = socket(AF_INET, SOCK_STREAM, 0)) > 0) { printf("Socket creation successfuln"); } else { printf("Socket creation failedn"); } } struct sockaddr_in getTargetAddress(char * ip, int port) { struct sockaddr_in ret; ret.sin_family = AF_INET; ret.sin_addr.s_addr = inet_addr(ip); ret.sin_port = htons(15000); return ret; }
Edit 1
Commenting includes out:
I dont have any compiler errors, just a warning because int received
is not in use.
I comment that out because I tried a lot and wanted to clean it up before I post it here, but thought it could be important enough to keep it as a comment.
Maybe its included in another include? I will check that.
I test and write on windows right now, but finally it needs to run on linux too. I test the server above with a small tool in Autoit on windows on the same machine which connects to a server and do a GET request. The server got the GET, printed it in his console and send a reply back which the Autoit-client got and printed, so it worked once. Without the close Operation I can do it everytime.
Edit 2 – got answer for the server, client still not running
Server is running fine now, got the answer from: http://cs.baylor.edu/~donahoo/practical/CSockets/WindowsSockets.pdf
Moving from UNIX sockets to Windows sockets is fairly simple. Windows programs require a different set of include files, need initialization and deallocation of WinSock resources, use closesocket( ) instead of close( ), and use a different error reporting facility. However, the meat of the application is identical to UNIX.
Edit 3 – client working, but one minor question
Need to shorten the links because I’m not allowed to post that many links directly.
My mistake in try 1 was to bind the client struct to the same IP as the server. “127.0.0.1”(clientaddress) => “Pseudo” and its working.
mySocket = socket(AF_INET, SOCK_STREAM, 0) struct sockaddr_in serverAddress = getTargetAddress("127.0.0.1", 15000); struct sockaddr_in myAddress = getTargetAddress("Pseudo", 15000); bind(mySocket, (const struct sockaddr *) &myAddress, sizeof(myAddress)); connect(mySocket, (const struct sockaddr * )&serverAddress, sizeof(serverAddress)); send(mySocket, question, strlen(question), 0);
But I dont need to bind here by myself, connect does it if its not done, and it handles that its an unused address. pubs.opengroup [.] org/onlinepubs/9699919799/functions/connect.html
If the socket has not already been bound to a local address, connect() shall bind it to an address which, unless the socket’s address family is AF_UNIX, is an unused local address.
mySocket = socket(AF_INET, SOCK_STREAM, 0) struct sockaddr_in serverAddress = getTargetAddress("127.0.0.1", 15000); connect(mySocket, (const struct sockaddr * )&serverAddress, sizeof(serverAddress)); send(mySocket, question, strlen(question), 0);
Of course this is working, but in my opinion not correct.
mySocket = socket(AF_INET, SOCK_STREAM, 0) struct sockaddr_in serverAddress = getTargetAddress("127.0.0.1", 15000); connect(mySocket, (const struct sockaddr * )&serverAddress, sizeof(serverAddress)); sendto(mySocket, question, strlen(question), 0, (const struct sockaddr *) &serverAddress, sizeof(serverAddress));
This here should also work in my opinion, I shouldnt need connect in this structure because it should be built in sendto.
pubs.opengroup [.] org/onlinepubs/9699919799/functions/connect.html
The connect() function shall attempt to make a connection on a connection-mode socket[…]
pubs.opengroup [.] org/onlinepubs/9699919799/functions/sendto.html
If the socket is connection-mode, dest_addr shall be ignored.
Because of the text above I think this should also work, but it doesnt. Maybe someone can say why? (Or maybe it should work without myAddress and bind)
mySocket = socket(AF_INET, SOCK_STREAM, 0) struct sockaddr_in serverAddress = getTargetAddress("127.0.0.1", 15000); struct sockaddr_in myAddress = getTargetAddress("Pseudo", 15000); bind(mySocket, (const struct sockaddr *) &myAddress, sizeof(myAddress)); sendto(mySocket, question, strlen(question), 0, (const struct sockaddr *) &serverAddress, sizeof(serverAddress));
And btw the return value for send and sendto isnt clearly.
Successful completion of a call to send() does not guarantee delivery of the message. A return value of -1 indicates only locally-detected errors.
Successful completion of a call to sendto() does not guarantee delivery of the message. A return value of -1 indicates only locally-detected errors.
I think the return value is useless, or not? If its -1 it can be delivered, if 1 it maybe isnt. Maybe determine another protocol?
minor questions
- Why I still need connect for sendto?
- Can I have a clear return value from send / sendto with another protocol?
Will search for both and edit it here if I found an answer, will still watch if someone can answer this. My major-problems are gone so really thanks to all.
Thanks for reading!
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Answer
It won’t work because you never call connect(). You should check return value from calls like connect() , send () etc.
The solution : You should call connect after you created the socket.
connect(mySocket, (SOCKADDR *)&serverAddress, sizeof(sockaddr_in));
To use send or sendTo with TCP, the socket has be connected or you will get an error.
send(mySocket, question, strlen(question), 0);