C sockets, chat server and client, problem echoing back.
- by wretrOvian
Hi
This is my chat server :
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <string.h>
#define LISTEN_Q 20
#define MSG_SIZE 1024
struct userlist {
int sockfd;
struct sockaddr addr;
struct userlist *next;
};
int main(int argc, char *argv[]) {
// declare.
int listFD, newFD, fdmax, i, j, bytesrecvd;
char msg[MSG_SIZE], ipv4[INET_ADDRSTRLEN];
struct addrinfo hints, *srvrAI;
struct sockaddr_storage newAddr;
struct userlist *users, *uptr, *utemp;
socklen_t newAddrLen;
fd_set master_set, read_set;
// clear sets
FD_ZERO(&master_set);
FD_ZERO(&read_set);
// create a user list
users = (struct userlist *)malloc(sizeof(struct userlist));
users->sockfd = -1;
//users->addr = NULL;
users->next = NULL;
// clear hints
memset(&hints, 0, sizeof hints);
// prep hints
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_flags = AI_PASSIVE;
// get srver info
if(getaddrinfo("localhost", argv[1], &hints, &srvrAI) != 0) {
perror("* ERROR | getaddrinfo()\n");
exit(1);
}
// get a socket
if((listFD = socket(srvrAI->ai_family, srvrAI->ai_socktype, srvrAI->ai_protocol)) == -1) {
perror("* ERROR | socket()\n");
exit(1);
}
// bind socket
bind(listFD, srvrAI->ai_addr, srvrAI->ai_addrlen);
// listen on socket
if(listen(listFD, LISTEN_Q) == -1) {
perror("* ERROR | listen()\n");
exit(1);
}
// add listfd to master_set
FD_SET(listFD, &master_set);
// initialize fdmax
fdmax = listFD;
while(1) {
// equate
read_set = master_set;
// run select
if(select(fdmax+1, &read_set, NULL, NULL, NULL) == -1) {
perror("* ERROR | select()\n");
exit(1);
}
// query all sockets
for(i = 0; i <= fdmax; i++) {
if(FD_ISSET(i, &read_set)) { // found active sockfd
if(i == listFD) { // new connection
// accept
newAddrLen = sizeof newAddr;
if((newFD = accept(listFD, (struct sockaddr *)&newAddr, &newAddrLen)) == -1) {
perror("* ERROR | select()\n");
exit(1);
}
// resolve ip
if(inet_ntop(AF_INET, &(((struct sockaddr_in *)&newAddr)->sin_addr), ipv4, INET_ADDRSTRLEN) == -1) {
perror("* ERROR | inet_ntop()");
exit(1);
}
fprintf(stdout, "* Client Connected | %s\n", ipv4);
// add to master list
FD_SET(newFD, &master_set);
// create new userlist component
utemp = (struct userlist*)malloc(sizeof(struct userlist));
utemp->next = NULL;
utemp->sockfd = newFD;
utemp->addr = *((struct sockaddr *)&newAddr);
// iterate to last node
for(uptr = users; uptr->next != NULL; uptr = uptr->next) {
}
// add
uptr->next = utemp;
// update fdmax
if(newFD > fdmax)
fdmax = newFD;
}
else { // existing sockfd transmitting data
// read
if((bytesrecvd = recv(i, msg, MSG_SIZE, 0)) == -1) {
perror("* ERROR | recv()\n");
exit(1);
}
msg[bytesrecvd] = '\0';
// find out who sent?
for(uptr = users; uptr->next != NULL; uptr = uptr->next) {
if(i == uptr->sockfd)
break;
}
// resolve ip
if(inet_ntop(AF_INET, &(((struct sockaddr_in *)&(uptr->addr))->sin_addr), ipv4, INET_ADDRSTRLEN) == -1) {
perror("* ERROR | inet_ntop()");
exit(1);
}
// print
fprintf(stdout, "%s\n", msg);
// send to all
for(j = 0; j <= fdmax; j++) {
if(FD_ISSET(j, &master_set)) {
if(send(j, msg, strlen(msg), 0) == -1)
perror("* ERROR | send()");
}
}
} // handle read from client
} // end select result handle
} // end looping fds
} // end while
return 0;
}
This is my client:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <string.h>
#define MSG_SIZE 1024
int main(int argc, char *argv[]) {
// declare.
int newFD, bytesrecvd, fdmax;
char msg[MSG_SIZE];
fd_set master_set, read_set;
struct addrinfo hints, *srvrAI;
// clear sets
FD_ZERO(&master_set);
FD_ZERO(&read_set);
// clear hints
memset(&hints, 0, sizeof hints);
// prep hints
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_flags = AI_PASSIVE;
// get srver info
if(getaddrinfo(argv[1], argv[2], &hints, &srvrAI) != 0) {
perror("* ERROR | getaddrinfo()\n");
exit(1);
}
// get a socket
if((newFD = socket(srvrAI->ai_family, srvrAI->ai_socktype, srvrAI->ai_protocol)) == -1) {
perror("* ERROR | socket()\n");
exit(1);
}
// connect to server
if(connect(newFD, srvrAI->ai_addr, srvrAI->ai_addrlen) == -1) {
perror("* ERROR | connect()\n");
exit(1);
}
// add to master, and add keyboard
FD_SET(newFD, &master_set);
FD_SET(STDIN_FILENO, &master_set);
// initialize fdmax
if(newFD > STDIN_FILENO)
fdmax = newFD;
else
fdmax = STDIN_FILENO;
while(1) {
// equate
read_set = master_set;
if(select(fdmax+1, &read_set, NULL, NULL, NULL) == -1) {
perror("* ERROR | select()");
exit(1);
}
// check server
if(FD_ISSET(newFD, &read_set)) {
// read data
if((bytesrecvd = recv(newFD, msg, MSG_SIZE, 0)) < 0 ) {
perror("* ERROR | recv()");
exit(1);
}
msg[bytesrecvd] = '\0';
// print
fprintf(stdout, "%s\n", msg);
}
// check keyboard
if(FD_ISSET(STDIN_FILENO, &read_set)) {
// read data from stdin
if((bytesrecvd = read(STDIN_FILENO, msg, MSG_SIZE)) < 0) {
perror("* ERROR | read()");
exit(1);
}
msg[bytesrecvd] = '\0';
// send
if((send(newFD, msg, bytesrecvd, 0)) == -1) {
perror("* ERROR | send()");
exit(1);
}
}
}
return 0;
}
The problem is with the part where the server recv()s data from an FD, then tries echoing back to all [send() ]; it just dies, w/o errors, and my client is left looping :(
