I have a simple question for you. I'm trying to make a simple client-server program. I want to connect the client to the server but I get the following error: Can't connect to the server. I'm new with this and this is why I can;t figure out what the problem is. Please give me some hints. Here is my client/server code:
Client:
#include<sys/socket.h>
#include<netinet/in.h>
#include<stdio.h>
#include<string.h>
#include<stdint.h>
int main(){
int socketc;
int connectnr;
int c;
struct sockaddr_in server;
char buffer[256];
socketc = socket(PF_INET, SOCK_STREAM, 0);
if(socketc < 0){
fprintf(stderr, "Error: Can't create client socket.\n");
return 1;
}
memset(&server, 0, sizeof(server));
server.sin_family = AF_INET;
server.sin_port = htons(4321);
server.sin_addr.s_addr = inet_addr("127.0.0.1");
connectnr = connect(c, (struct sockaddr *) & server, sizeof(struct sockaddr_in));
if(connectnr < 0){
printf("connectnr %d: \n", connectnr);
fprintf(stderr, "Error: Can't connect to the server.\n");
return 1;
}
close(c);
}
Server:
#include<sys/socket.h>
#include<netinet/in.h>
#include<stdio.h>
#include<string.h>
#include<stdint.h>
#include<signal.h>
#include<unistd.h>
#include<stdlib.h>
int c;
int main(){
int connsocket;
int bindcod;
int l;
struct sockaddr_in client, server;
connsocket = socket(PF_INET, SOCK_STREAM, 0);
if(connsocket < 0){
fprintf(stderr, "Error: Can't create the server socket.\n");
return 1;
}
memset(&server, 0, sizeof(server));
server.sin_family = AF_INET;
server.sin_port = htons(4321);
server.sin_addr.s_addr = INADDR_ANY;
bindcod = bind(connsocket, (struct sockaddr *) &server, sizeof(struct sockaddr_in));
if(bindcod < 0){
fprintf(stderr, "Error: Con't establish the bind. Port is already used.\n");
return 1;
}
listen(connsocket, 5);
while(1){
memset(&client, 0, sizeof(client));
l = sizeof(client);
printf("Waiting for the client to connect,\n");
c = accept(connsocket, (struct sockaddr *) &client, &l);
printf("New client connected with address %s and port %d.\n", inet_ntoa(client.sin_addr), ntohs(client.sin_port));
}
}
You are giving wrong socket to connect function.
Replace
connect(c, (struct sockaddr *) & server, sizeof(struct sockaddr_in));
with
connect(socketc , (struct sockaddr *) & server, sizeof(struct sockaddr_in));
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 writing a simple tcp echo client server code both my client and server code are running on the same machine i did bind two different addresses to client and server but client ip address is not getting printed when connected to server i changed addresses and still i was not able to print address i don't see any mistake in code.Is this my os issue or am i making some mistake.
my server code:
#include<stdio.h>
#include<stdlib.h>
#include<sys/socket.h>
#include<sys/types.h>
#include<string.h>
#include<netinet/in.h>
#define ERROR -1
#define MAX_CLIENTS 10
#define MAX_DATA 1024
int main(int argc, char *argv[]){
struct sockaddr_in server;
struct sockaddr_in client;
int sock;
int new;
int sockaddr_len = sizeof(struct sockaddr_in);
int data_len;
char data[MAX_DATA+1];
if((sock = socket(AF_INET,SOCK_STREAM,0)) == ERROR){
perror("server socket");
exit(-1);
}
server.sin_family = AF_INET;
server.sin_port = htons(atoi(argv[1]));
inet_aton(argv[2],&server.sin_addr.s_addr);
bzero(&server.sin_zero,0);
if(bind(sock, (struct sockaddr *)&server,sockaddr_len) == ERROR){
perror("bind");
exit(-1);
}
if(listen(sock, MAX_CLIENTS) == ERROR){
perror("listen");
exit(-1);
}
while(1){
if((new = accept(sock,(struct sockaddr *)&client,&sockaddr_len)) == ERROR){
perror("accept");
exit(-1);
}
//ip not getting printed
printf("New client connected from port no %d IP %s\n",ntohs(client.sin_port),inet_ntoa(client.sin_addr.s_addr));
data_len = 1;
while(data_len){
data_len = recv(new,data,MAX_DATA,0);
if(data_len){
send(new, data, data_len,0);
data[data_len] = '\0';
printf("Sent message: %s", data);
}
}
printf("Client disconnected\n");
close(new);
}
}
my client code:
#include<stdio.h>
#include<stdlib.h>
#include<sys/socket.h>
#include<sys/types.h>
#include<string.h>
#include<netinet/in.h>
#define ERROR -1
#define BUFFER 1024
int main(int argc, char *argv[]){
struct sockaddr_in remote_server,client;
int sock,len;
char input[BUFFER];
char output[BUFFER+1];
client.sin_family = AF_INET;
client.sin_port = htons(3000);
inet_aton("127.0.2.8",&client.sin_addr.s_addr);
bzero(&client.sin_zero,0);
if((sock = socket(AF_INET,SOCK_STREAM,0)) == ERROR){
perror("socket");
exit(-1);
}
int size = sizeof(struct sockaddr_in);
if(bind(sock, (struct sockaddr *)&client,size) == ERROR){
perror("bind");
exit(-1);
}
remote_server.sin_family = AF_INET;
remote_server.sin_port = htons(atoi(argv[2]));
remote_server.sin_addr.s_addr = inet_addr(argv[1]);
bzero(&remote_server.sin_zero , 0);
if((connect(sock ,(struct sockaddr *)&remote_server , sizeof(struct sockaddr_in))) == ERROR){
perror("connect");
exit(-1);
}
while(1){
fgets(input, BUFFER, stdin);
send(sock, input, strlen(input) , 0);
len = recv(sock,output,BUFFER,0);
output[len] = '\0';
printf("%s\n",output);
}
close(sock);
}
This is the output:
New client connected from port no 3000 and IP
First of all you need two more includes in client as well as server
#include<arpa/inet.h> // for inet_aton(), inet_addr() and inet_ntoa()
#include<unistd.h> //for close()
Secondly,
The function declaration for inet_aton() and inet_ntoa() are respectively:
int inet_aton(const char *cp, struct in_addr *inp);
and
char *inet_ntoa(struct in_addr in);
So, You must pass the entire structure i.e xyzaddr.sin_addr instead of xyzaddr.sin_addr.s_addr(which is an int)
Hence make these changes as well:
In server:
inet_aton(argv[2],&server.sin_addr.s_addr); -> inet_aton(argv[2],&server.sin_addr);
inet_ntoa(client.sin_addr.s_addr) -> inet_ntoa(client.sin_addr)
In client:
inet_aton("127.0.2.8",&client.sin_addr.s_addr); -> inet_aton("127.0.2.8",&client.sin_addr);
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 have a problem with my code about web server
#include<netinet/in.h>
#include<stdio.h>
#include<stdlib.h>
#include<sys/socket.h>
#include<sys/stat.h>
#include<sys/types.h>
#include<unistd.h>
int main() {
int create_socket, new_socket;
socklen_t addrlen;
int bufsize = 1024;
char *buffer = malloc(bufsize);
struct sockaddr_in address;
if ((create_socket = socket(AF_INET, SOCK_STREAM, 0)) > 0){
printf("The socket was created\n");
}
address.sin_family = AF_INET;
address.sin_addr.s_addr = INADDR_ANY;
address.sin_port = htons(15000);
if (bind(create_socket, (struct sockaddr *) &address, sizeof(address)) == 0){
printf("Binding Socket\n");
}
while (1) {
if (listen(create_socket, 10) < 0) {
perror("server: listen");
exit(1);
}
if ((new_socket = accept(create_socket, (struct sockaddr *) &address, &addrlen)) < 0) {
perror("server: accept");
exit(1);
}
if (new_socket > 0){
printf("The Client is connected...\n");
}
recv(new_socket, buffer, bufsize, 0);
printf("%s\n", buffer);
write(new_socket, "hello world\n", 12);
close(new_socket);
}
close(create_socket);
return 0;
}
this is a little code to create a web server that at the port 15000 reply with "hello wordl" . Now i would that my server at a request (for example) "http://127.0.0.1:15000/luigi" reply with the text "luigi",that is with the phrase after " / ". Thanks!
After recv function, you will have something like
GET /luigi HTTP/1.1
in buffer.This is the request sent by browser.
Text after GET is the relative url to your base address (127.0.0.1:15000). Now you can parse the buffer and do whatever you want.You can go to http://www.w3.org/Protocols/rfc2616/rfc2616-sec5.html for more details.
To add up to what user3864685 said, you can use 'strtok' function to get the string after "GET /".
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");