Server client program bind function issue - c

Question

I am implementing server client program where the both the ports user define
in server side user will insert server port number using command line interface
in client side user will insert client port id and then followed by serve port id.
I got stuck for a long time finding out what is wrong with my server client program. The issue is in binding though but I tried whatever possible way to implement it.
Server.c
#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<sys/socket.h>
#include<sys/types.h>
#include<netdb.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<string.h>
#include<strings.h>
void error(char *msg){
perror(msg);
exit(1);
}
int main(int argc, char *argv[]){
int sockfd, newsockfd, clilen;
char buffer[256];
struct sockaddr_in serv_addr, cli_addr;
int n;
if(argc < 2){
fprintf(stderr,"error!!! no port provided\n");
exit(1);
}
bzero((char *) &serv_addr, sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = INADDR_ANY;
serv_addr.sin_port = htons(atoi(argv[1]));
if ((bind(sockfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr))) != 0) {
printf("socket bind failed...\n");
exit(0);
}
listen(sockfd, 5);
while(1){
clilen = sizeof(cli_addr);
newsockfd = accept(sockfd, (struct sockaddr*)&cli_addr, &clilen);
if(newsockfd < 0){
error("ERROR on accept");
exit(1);
}
printf("New client connected from port no %d and IP %s\n", ntohs(cli_addr.sin_port), inet_ntoa(cli_addr.sin_addr));
bzero(buffer, 256);
n = read(newsockfd, buffer, 255);
if(n < 0){
error("ERROR reading from socket");
exit(1);
}
}
printf("Here is the message: %s \n",buffer);
n = write(newsockfd, "I got your message", 18);
if(n < 0){
error("ERROR writing from socket");
exit(1);
}
return (0);
}
Client.c
#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<sys/socket.h>
#include<sys/types.h>
#include<netdb.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<string.h>
#include<strings.h>
void error(char *msg){
perror(msg);
exit(1);
}
int main(int argc, char *argv[]){
int sockfd, n;
struct sockaddr_in serv_addr;
char buffer[256];
if(argc < 3){
fprintf(stderr,"usage %s hostname port\n",argv[0]);
exit(0);
}
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if(sockfd < 0){
error("ERROR opening socket");
exit(1);
}
bzero((char *) &serv_addr, sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(atoi(argv[2]));
serv_addr.sin_addr.s_addr = inet_addr(argv[1]);
if(connect(sockfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) < 0){
error("ERROR connecting");
exit(1);
}
printf("Please enter the message: ");
bzero(buffer, 256);
fgets(buffer, 256, stdin);
n = write(sockfd, buffer, strlen(buffer));
if(n < 0){
error("ERROR writing to socket");
exit(1);
}
bzero(buffer, 256);
n = read(sockfd, buffer, 255);
if(n < 0){
error("ERROR reading from socket");
exit(1);
}
printf("%s\n",buffer);
return (0);
}
Terminal where client is running
Terminal where server is running.

Answer 1

The server never creates a socket. sockfd is an uninitialized, indeterminate value when passed to bind.
Turning up your compiler's warning level may have alerted you to this:
server.c:36:14: warning: ‘sockfd’ may be used uninitialized [-Wmaybe-uninitialized]
36 | if ((bind(sockfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr))) != 0) {
| ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Obtain a valid file descriptor before trying to bind.
if (-1 == (sockfd = socket(...)) {
perror("socket");
return 1;
}
Consider the use of getaddrinfo to establish your sockets. The man page as well as Beej's Guide to Network Programming have various examples.
Additionally, the code that responds to the client
printf("Here is the message: %s \n",buffer);
n = write(newsockfd, "I got your message", 18);
if(n < 0){
error("ERROR writing from socket");
exit(1);
}
is outside of the loop that handles incoming connections.