Here are working Server and Client applications. Study them to glean some ideas.
Server.c:
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
void handleClient(int client);
int main(int argc, char** argv)
{
if (argc != 2)
{
fprintf(stderr, "Usage: %s <port>\n", argv[0]);
exit(EXIT_FAILURE);
}
const char* PORT = argv[1];
// open socket
int sockfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (sockfd == -1)
{
perror("Cannot open socket");
exit(EXIT_FAILURE);
}
// bind socket
struct sockaddr_in sin;
memset(&sin, 0, sizeof(sin));
sin.sin_family = AF_INET;
sin.sin_addr.s_addr = htonl(INADDR_ANY);
sin.sin_port = htons(atoi(PORT));
int ret = bind(sockfd, (struct sockaddr*) &sin, sizeof(sin));
if (ret != 0)
{
perror("Cannot bind socket");
exit(EXIT_FAILURE);
}
// setup listen
ret = listen(sockfd, 5);
if (ret != 0)
{
perror("Cannot setup listen");
exit(EXIT_FAILURE);
}
for (;;)
{
// accept client connection
int client = accept(sockfd, NULL, NULL);
printf("Client connected.\n");
handleClient(client);
}
close(sockfd);
return 0;
}
void handleClient(int client)
{
char buf[1024];
for (;;)
{
int bytes_rcvd = recv(client, buf, sizeof(buf) - 1, 0);
if (bytes_rcvd > 0)
{
buf[bytes_rcvd] = '\0';
fprintf(stdout, "Server Received: %s\n", buf);
// send message back to client
const char* msg = "Your message was received.";
const size_t msg_len = strlen(msg);
size_t bytes_sent = 0;
while (bytes_sent < msg_len)
{
int ret = send(client, msg + bytes_sent, msg_len - bytes_sent, 0);
if (ret > 0)
{
bytes_sent += ret;
}
else if (ret < 0)
{
perror("Error sending data to client.");
}
}
}
else if (bytes_rcvd == 0)
{
printf("Client disconnected.\n");
break; // client disconnected
}
else
{
perror("Error receiving from client.");
}
}
close(client);
}
Client.c:
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
void stripNewline(char* str);
int main(int argc, char** argv)
{
if (argc != 3)
{
fprintf(stderr, "Usage: %s <host> <port>\n", argv[0]);
exit(EXIT_FAILURE);
}
const char* HOST = argv[1];
const char* PORT = argv[2];
// open socket
int sockfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (sockfd == -1)
{
perror("Cannot open socket");
exit(EXIT_FAILURE);
}
// connect socket
struct sockaddr_in sin;
memset(&sin, 0, sizeof(sin));
sin.sin_family = AF_INET;
sin.sin_addr.s_addr = inet_addr(HOST);
sin.sin_port = htons(atoi(PORT));
int ret = connect(sockfd, (struct sockaddr*) &sin, sizeof(sin));
if (ret != 0)
{
perror("Cannot connect socket");
exit(EXIT_FAILURE);
}
for (;;)
{
char msg[1024];
printf("Enter the message to send: ");
fgets(msg, sizeof(msg), stdin);
stripNewline(msg);
send(sockfd, msg, strlen(msg), 0);
int bytes_rcvd = recv(sockfd, msg, sizeof(msg) - 1, 0);
if (bytes_rcvd > 0)
{
msg[bytes_rcvd] = '\0';
printf("Client Received: %s\n\n", msg);
}
else if (bytes_rcvd == 0)
{
fprintf(stderr, "Server gave us the boot!\n");
break;
}
else
{
perror("Error receiving.");
}
}
close(sockfd);
return 0;
}
void stripNewline(char* str)
{
char* nl = strchr(str, '\n');
if (nl)
{
*nl = '\0';
}
}