#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

struct student{
    char indeks[6];
    char nazwisko[20];
};

typedef struct student student;

int main(int argc, char** argv) {

    student tab[2];
    strcpy(tab[0].indeks, "132244");
    strcpy(tab[0].nazwisko, "Tomasz Jurek      \n");
    strcpy(tab[1].indeks, "136731");
    strcpy(tab[1].nazwisko, "Hubert Kamieniarz\n");

    struct sockaddr_in saddr, caddr;
    int sfd, cfd, on = 1, i = 0, cmpres;
    socklen_t len;

    sfd = socket(PF_INET, SOCK_STREAM, 0);
    setsockopt(sfd, SOL_SOCKET, SO_REUSEADDR, (char*)&on, sizeof(on));

    saddr.sin_family = PF_INET;
    saddr.sin_port = htons(3210);
    saddr.sin_addr.s_addr = INADDR_ANY;
    bind(sfd, (struct sockaddr*)&saddr, sizeof(saddr));
    listen(sfd, 10);
    char buf[32];

    while(1) {
        len = sizeof(caddr);
        cfd = accept(sfd, (struct sockaddr*)&caddr, &len);
        printf("New connection from: %s:%d\n", inet_ntoa(caddr.sin_addr), caddr.sin_port);
        read(cfd, buf, sizeof(buf));
        for(i=0; i<2; i++)
        {
            cmpres = strncmp(buf, tab[i].indeks, 6);
            if(cmpres==0) {
                write(cfd, tab[i].nazwisko, sizeof(tab[i].nazwisko));
                break;
            }
        }
        if(cmpres!=0) write(cfd, "ERROR!\n", 6);
        close(cfd);
    }

    close(sfd);

    return 0;
}



===========================================================


#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main(int argc, char** argv) {

int fd = socket(PF_INET, SOCK_STREAM, 0);

struct sockaddr_in addr;
struct hostent *host;

addr.sin_family = PF_INET;
addr.sin_port = htons(atoi(argv[2]));

host = gethostbyname(argv[1]);

memcpy(&addr.sin_addr.s_addr, host->h_addr, host->h_length);

connect(fd, (struct sockaddr*)&addr, sizeof(addr));

char buf[256];
int rc = read(fd, buf, sizeof(buf));
write(1, buf, rc);

close(fd);

return 0;
}



================================================


#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main(int argc, char** argv) {

struct sockaddr_in saddr, caddr;
int sfd, cfd, on = 1;
socklen_t len;

sfd = socket(PF_INET, SOCK_STREAM, 0);
setsockopt(sfd, SOL_SOCKET, SO_REUSEADDR, (char*)&on, sizeof(on));

saddr.sin_family = PF_INET;
saddr.sin_port = htons(3210);
saddr.sin_addr.s_addr = INADDR_ANY;
bind(sfd, (struct sockaddr*)&saddr, sizeof(saddr));
listen(sfd, 10);

while(1) {
    len = sizeof(caddr);
    cfd = accept(sfd, (struct sockaddr*)&caddr, &len);
    printf("New connection from: %s:%d\n", inet_ntoa(caddr.sin_addr), caddr.sin_port);
    write(cfd, "Hello there!\n", 14);
    close(cfd);
}

close(sfd);

return 0;
}