First try with socket prog. any help why I get this error? This my server side code, till the part of bind (exluding listen etc)
thnx in advance
int main(){
unsigned int s; //returned by socket()
int port; //port number
int n; //fore read() & write()
int newsockfd; //returned by accept()
struct sockaddr_in server , client;
socklen_t clntLen; // Length of client address data structure
s = socket(AF_UNIX, SOCK_STREAM,0);
if(s==-1){
perror("Socket was not created\n");
return 0;
}
printf("Socket successfully created! ID: %d\n",s);
//sockaddr_in structure
memset( &server, 0, sizeof(server) ); // Zero structure
server.sin_family = AF_INET;
server.sin_addr.s_addr = htonl(INADDR_ANY);
server.sin_port = htons( 8888 );
//Bind
if( bind(s,(struct sockaddr *)&server , sizeof(server)) < 0){
//print the error message
perror("Bind failed! Error");
return 1;
}
printf("Bind completed successfully\n");
}
Use AF_INET instead of AF_UNIX in the call to socket().
Related
I am fairly new to socket programming. I saw a tutorial and tried implementing the programs in my Linux machine. The codes are :
CLIENT :
int main() {
char buf[256] = "In client";
// create the socket
int sock;
sock = socket(AF_INET, SOCK_STREAM, 0);
//setup an address
struct sockaddr_in server_address;
server_address.sin_family = AF_INET;
server_address.sin_addr.s_addr = INADDR_ANY;
server_address.sin_port = htons(9002);
int status = connect(sock, (struct sockaddr *) &server_address, sizeof(server_address));
if(status == -1)
{
printf("There Was an error!");
}
recv(sock, buf, sizeof(buf), 0);
printf("\n %s \n", buf);
close(sock);
return 0;
}
SERVER:
int main() {
char server_message[256] = "You have reached the server!";
// create the server socket
int server_socket;
server_socket = socket(AF_INET, SOCK_STREAM, 0);
// define the server address
struct sockaddr_in server_address;
server_address.sin_family = AF_INET;
server_address.sin_port = htons(9002);
server_address.sin_addr.s_addr = INADDR_ANY;
// bind the socket to our specified IP and port
bind(server_socket, (struct sockaddr*) &server_address, sizeof(server_address));
listen(server_socket, 5);
int client_socket;
client_socket = accept(server_socket, NULL, NULL);
// send the message
send(client_socket, server_message, sizeof(server_message), 0);
// close the socket
close(server_socket);
return 0;
}
The code is self-explanatory. When I run the server and then the client, for the first time, it works. But when I do it again, just after the previous one, the Client gives the message - There Was an error!, that means the connection is not happening.
Can anyone help why is this occurring?
Thanks in advance!
You should be checking for errors for all system calls in your server. I'm guessing that your bind is failing, because the port is "already in use". The reason for this is that the connection from the previous instance of the server lingers for a while in the operating system's connection table.
You want to use setsockopt with SO_REUSEADDR to avoid the bind failure. Specifically, add this prior to the bind call.
int reuse = 1;
if (setsockopt(server_socket, SOL_SOCKET, SO_REUSEADDR, (const char*)&reuse, sizeof(reuse)) < 0)
perror("setsockopt(SO_REUSEADDR) failed");
(And do check errors. Makes debugging these kinds of things much easier if you know when something fails. Also, use perror or strerror(errno) in order to find out exactly why it failed -- not just that it failed.)
Check out my whole code here and see how it runs.
This is the server
int main(){
SOCKET s, newsocket;
struct sockaddr_in server, client;
int receiving;
char clientMessage[2000], *message;
if((s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == INVALID_SOCKET){
printf("socker error at %d", GetLastError());
}else{
puts("socket created");
}
server.sin_addr.s_addr = inet_addr("127.0.0.1");
server.sin_family = AF_INET;
server.sin_port = htons(8080);
if(bind(s, (struct sockaddr*)&server, sizeof(server)) < 0){
printf("err at binding %d", GetLastError());
}else{
puts("binded.");
}
listen(s, 3);
puts("listening to connections...");
int c = sizeof(struct sockaddr_in);
while((newsocket = accept(s, (struct sockaddr*)&client, &c)) != INVALID_SOCKET){
puts("connection accepted");
//send
message="hello client";
send(newsocket, message, strlen(message), 0);
recv(newsocket, clientMessage, 50, 0);
puts(clientMessage);
}
puts("waiting for a machine");
if(newsocket == INVALID_SOCKET){
printf("newsocket invalid at %d", GetLastError());
}
getchar();
closesocket(s);
WSACleanup();
}
This is the client
int main(){
SOCKET s;
struct sockaddr_in server;
if((s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == INVALID_SOCKET){
printf("socket error At %d", GetLastError());
}else{
puts("socket initialised");
}
server.sin_port = htons(8080);
server.sin_family = AF_INET;
server.sin_addr.s_addr = inet_addr("176.40.201.72");
printf("server values are defined.. \n");
printf("connecting..\n");
if(connect(s, (struct sockaddr*)&server, sizeof(server)) < 0){
printf("connection error %d" , GetLastError());
}else{
puts("connected");
}
return 0;
}
I am trying to make a TCP Socket Server in C that stores the data that the clients are sending to the server in a struct array. Well, so far, so good. When i am printing the values of the struct, only the last value(key) is stored in all the positions of the struct array!
Why is that? Thanks in advance!
Client Code:
int main(int argc , char *argv[])
{
int sock;
struct sockaddr_in server;
//Create socket
sock = socket(AF_INET , SOCK_STREAM , 0);
char *p;
server.sin_addr.s_addr = inet_addr(argv[1]);
int port = strtol(argv[2], &p, 10);
server.sin_port = htons(port);
server.sin_family = AF_INET;
//Connect to remote server
if (connect(sock , (struct sockaddr *)&server , sizeof(server)) < 0)
{
perror("connect failed. Error");
return 1;
}
write(sock , argv[3] ,strlen(argv[3])+1); //send the 3rd argument(which is the input key)
close(sock);
return 0;
}
Server Code:
struct key_store
{
char *key;
}store[1024];
int STORED=0;
void handler(int socket_desc)
{
int client_sock;
char client_message[1024];
client_sock = accept(socket_desc, (struct sockaddr *) NULL, NULL);
printf("Connection accepted\n");
while( read(client_sock , client_message , 100) > 0 )
{
store[STORED].key=client_message;
STORED++;
}
close(client_sock);
}
int main(int argc , char *argv[])
{
int socket_desc;
struct sockaddr_in server;
server.sin_port = htons( 8888 );
//Create socket
socket_desc = socket(AF_INET , SOCK_STREAM , 0);
if (socket_desc == -1)
{
printf("Could not create socket");
}
printf("Socket created\n");
//Prepare the sockaddr_in structure
server.sin_addr.s_addr = inet_addr("127.0.0.1");
server.sin_family = AF_INET;
//Bind
if( bind(socket_desc,(struct sockaddr *)&server , sizeof(server)) < 0)
{
//print the error message
perror("bind failed. Error");
return 1;
}
printf("bind done\n");
//Listen
listen(socket_desc , 5);
int count =0;
while(count < 3)
{
handler(socket_desc);
count++;
}
close(socket_desc);
for (int i=0;i<STORED;i++)
{
printf("KEY --> %s\n",store[i].key); //print the store keys
}
return 0;
}
Input:
./client 127.0.0.1 8888 123456
./client 127.0.0.1 8888 testkey
./client 127.0.0.1 8888 2017
Output:
./server
Socket created
bind done
Connection accepted
Connection accepted
Connection accepted
KEY --> 2017
KEY --> 2017
KEY --> 2017
you are storing a pointer to client_message in your store. Next message will overwrite that buffer. You have to make a copy of the message before you store it
try
put(strdup(client_message));
You have all sorts of other issues, but this will at least move you forward
This is a simple iterative client-server program. Where the server prints out "Received request" on successful establishment of connection.
server side
#define LENGTH 256
#define SERV_PORT 4000
#define LISTENQ 8
int main()
{
int listenfd, connfd, n;
socklen_t clilen;
char buf[LENGTH];
struct sockaddr_in cliaddr, servaddr;
//creation of socket
listenfd = socket (AF_INET, SOCK_STREAM, 0);
//creating socket address
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
servaddr.sin_port = htons(SERV_PORT);
bind (listenfd, (struct sockaddr *) &servaddr, sizeof(servaddr));
// printf("\nServer running.. waiting for connections");
// listen(listenfd, LISTENQ);
for(; ;)
{
clilen = sizeof(cliaddr);
connfd = accept(listenfd, (struct sockaddr *) &cliaddr, &clilen);
printf("\nReceived request");
//sleep(5);
}
return 0;
}
client side
#define LENGTH 256
#define SERV_PORT 4000
int main( int argc, char *argv[])
{
int sock;
struct sockaddr_in server;
struct hostent *hp;
char buff[256];
sock = socket(AF_INET, SOCK_STREAM, 0);
if(sock < 0)
{
perror("socket failed");
exit(1);
}
server.sin_family = AF_INET;
hp = gethostbyname(argv[1]);
if(hp == 0)
{
perror("gethost by name failed");
exit(1);
}
memcpy(&server.sin_addr, hp->h_addr, hp->h_length);
server.sin_port = htons(4000);
if(connect(sock, (struct sockaddr *) &server, sizeof(server)) < 0)
{
perror("\nconnect failed");
exit(1);
}
return 0;
}
When I run this multiple client-server code, the output for first client is different from the preceding clients. I need the first client to output like others. Can someone help?
When the first client establishes a connection with the server, the server doesn't output "Received request", where as, for the other clients do output "Received request".
You need to restore the listen() call. – EJP
I created a server socket in C. This is the most basic stuff like what you would fine in a simple TCP server example. Server code is below. I also created a client socket that runs on the host machine. Code also below. However, for some reason the client is not able to connect to the server. The IP address I used is the same as the one under the entry eth0 from the "ip addr" command. The network adapter of the VM is a bridged connection.
The exact same code works when both client and server run on the same machine (the host).
Thank you!
Server code:
int sockfd;
int clientfd;
struct sockaddr_in self;
struct sockaddr_in client_addr;
int addrlen = sizeof (client_addr);
if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
perror("Socket");
return EXIT_FAILURE;
}
printf("Socket descriptor is: %d\n", sockfd);
memset(&self, 0, sizeof (self));
self.sin_family = AF_INET;
self.sin_port = htons(MY_PORT);
self.sin_addr.s_addr = INADDR_ANY;
if (bind(sockfd, (struct sockaddr*) &self, sizeof (self)) != 0) {
perror("socket--bind");
return EXIT_FAILURE;
}
if (listen(sockfd, 20) != 0) {
perror("socket--listen");
return EXIT_FAILURE;
}
clientfd = accept(sockfd, (struct sockaddr*) &client_addr, &addrlen);
printf("%s:%d connected\n", inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port));
Client Code:
int sock;
struct sockaddr_in server;
//struct sockaddr_in client;
struct hostent *hp;
//char buf[BUFFER_SIZE];
if ((sock = socket(AF_INET, SOCK_STREAM, 0)) < 0)
die(6, "Opening stream socket");
printf("Client socket file descriptor is: %d\n", sock);
memset(&server, (char) 0, sizeof (server));
server.sin_family = AF_INET;
hp = gethostbyname(host_name);
if (!hp) {
//sprintf(buf, "%s: unknown host\n", host_name);
die(8, "%s: unknown host\n", host_name);
}
memcpy(hp->h_addr, &server.sin_addr, hp->h_length);
server.sin_port = htons((u_short) SERVER_PORT);
/* Try to connect */
if ((connect(sock, (struct sockaddr *) &server, sizeof (server))) < 0)
die(7, "%s", "Failed to connect stream socket\n");
I am getting an error "Invalid argument" when i call the accept() function on the server side of a client-server application. I don't get what is wrong and if you see what is wrong let me know please. Thanks.
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
int main(int argc, char* argv[])
{
int sockfd, newsockfd, portno, len;
struct sockaddr_in server, client;
if(argc < 2){
perror("Add more arguments");
}
sockfd = socket(AF_UNIX,SOCK_STREAM,0);
if(sockfd < 0){
perror("Error at socket()");
}
printf("Socketfd: %d\n",sockfd);
bzero((char *)&server, sizeof(server));
portno = atoi(argv[1]);
server.sin_family = AF_UNIX;
server.sin_addr.s_addr = INADDR_ANY;
server.sin_port = htons(portno);
if(bind (sockfd, (struct sockaddr *)&server, sizeof(server)) <0){
perror("Error at bind ()-server");
}
listen(sockfd,5);
int readval;
char buffer[256];
for(;;){
len = sizeof(client);
newsockfd = accept (sockfd, (struct sockaddr *)&server,&len);
if (newsockfd == -1){
perror("Erroare at accept()");
}
else do{
readval = (sockfd,buffer,sizeof(buffer));
if (readval < 0 ){
perror("Error at reading()");
}
else if (readval == 0){
printf("End conection");
}
else{
printf("Mesage is: %s\n", buffer);
}
}while (readval > 0);
close(newsockfd);
}
return 0;
}
You have to use sockaddr_un instead of sockaddr_in for Unix domain sockets OR substitute AF_UNIX with AF_INET.
Plus, check the return of listen.
Plus change this line
readval = (sockfd,buffer,sizeof(buffer));
with
readval = read(newsockfd,buffer,sizeof(buffer));
because data is going to be sent through the newly created socket and not on the listening one
Plus, as mentioned by #trojanfoe, subst the server with the client structure into the accept() call
This line:
newsockfd = accept (sockfd, (struct sockaddr *)&server, &len);
Should be:
newsockfd = accept (sockfd, (struct sockaddr *)&client, &len);
From the manpage:
The argument addr is a pointer to a sockaddr structure. This structure
is filled in with the address of the peer socket, as known to the
communications layer. The exact format of the address returned addr is
determined by the socket's address family (see socket(2) and the
respective protocol man pages). When addr is NULL, nothing is filled
in; in this case, addrlen is not used, and should also be NULL.
Also check the return value from listen().
I ran into a similar issue before and it was due to not having the read function in a loop. Here is an example I did before.
while (1) {
new_sockfd = accept(sockfd, (struct sockaddr *) &client_addr,
&sin_size);
if (new_sockfd == -1)
perror("accepting connection");
printf("server: got connection from %s port %d\n",
inet_ntoa(client_addr.sin_addr),
ntohs(client_addr.sin_port));
recv_length = recv(new_sockfd, &buffer, DATA, 0);
while (recv_length > 0) {
printf("RECV: %d bytes\n", recv_length);
dump(buffer, recv_length);
recv_length = recv(new_sockfd, &buffer, DATA, 0);
}
close(new_sockfd);
}