linux下tcp,udp,icmp小例子

Tcp的

客户端#include <stdio.h>#include <string.h>#include <stdlib.h>#include <unistd.h>#include <sys/types.h>#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>#include <signal.h>#define MAXLINE 80int port = 8000;int main(int argc, char *argv[]){  struct sockaddr_in pin;  int sock_fd;  char buf[MAXLINE];  char str[MAXLINE];  int n;  signal(SIGPIPE,SIG_IGN);  bzero(&pin, sizeof(pin));  pin.sin_family = AF_INET;  inet_pton(AF_INET, argv[1], &pin.sin_addr);  pin.sin_port = htons(port);    sock_fd = socket(AF_INET, SOCK_STREAM, 0);  n=connect(sock_fd, (void *)&pin, sizeof(pin));  if (-1 == n)  {     perror("call connect");     exit(1);  }  while(NULL != fgets(str,MAXLINE, stdin))  {    write(sock_fd, str, strlen(str)+1);    n=read(sock_fd, buf, MAXLINE);    if (0 == n)      printf("the othere side has been closed.\n");    else      printf("receive from server:%s\n",buf);  }  close(sock_fd);  return 0;}服务器端#include <stdio.h>#include <string.h>#include <unistd.h>#include <ctype.h>#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>#include <errno.h>#include <stdlib.h>#include <signal.h>#define MAXLINE 8800int port = 8000;int main(void){    struct sockaddr_in sin;    struct sockaddr_in pin;    int listen_fd;    int conn_fd;    int sock_fd;    int nready;    int maxi;    int max;    int client[FD_SETSIZE];    int address_size = sizeof(pin);    char buf[MAXLINE];    char str[INET_ADDRSTRLEN];    int i;    int len;    int n;    int ret;    bzero(&sin, sizeof(sin));    sin.sin_family = AF_INET;    sin.sin_addr.s_addr = INADDR_ANY;    sin.sin_port = htons(port);    signal(SIGPIPE, SIG_IGN);    signal(SIGCHLD, SIG_IGN);    listen_fd = socket(AF_INET, SOCK_STREAM, 0);    if (-1 == listen_fd)    {        perror("call to socket");        exit(1);    }    n = bind(listen_fd, (struct sockaddr *)&sin, sizeof(sin));    if (-1 == n)    {        perror("call to bind");        exit(1);    }    n = listen(listen_fd, 20);    if (-1 == n)    {        perror("call to listen");        exit(1);    }    printf("Accepting connections...\n");    while(1)    {        conn_fd = accept(listen_fd, (struct sockaddr *)&pin, &address_size);        n = fork();        if (-1 == n){            perror("call to fork");            exit(1);        }        else if (0 == n)        {            close(listen_fd);            while(1)            {                memset(buf,'\0',MAXLINE);readagain:                ret = read(conn_fd,buf,MAXLINE);                printf("I read %d Byte!\n",ret);                if (-1 == ret){                    if (errno == EINTR){                        goto readagain;                    }else{                        perror("call to read");                        exit(1);                    }                } else if (0 == ret){                    printf("the other side has been closed.\n");                    break;                }                printf("you ip is %s at port %d:%s\n",                     inet_ntop(AF_INET, &pin.sin_addr,str,sizeof(str)),                     ntohs(pin.sin_port),buf);                /*    len = strlen(buf);                for (i = 0; i < len; i++)                {                    buf[i] = toupper(buf[i]);                }writeagain:                ret = write(conn_fd, buf, len+1);                printf("I write %d Byte!\n",ret);                if (-1 == ret){                    if (errno == EINTR){                        goto writeagain;                    } else {                        perror("call to write!");                        break;                    }                    }*/            }// end while                        ret = close(conn_fd);            if (-1 == ret){                perror("call close");                return -1;            }            exit(0);        }    }    return 0;}

Udp的

icmp的

#include <stdio.h>#include <sys/types.h>          /* See NOTES */#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>//#include <linux/icmp.h>#include <strings.h>#include <netinet/ip_icmp.h>#include <stdlib.h>void send_echo_req(int sockfd, struct sockaddr_in *dstaddr);  uint16_t in_cksum(uint16_t *addr, int len);  void recv_echo_reply(int sockfd);  void err_sys(const char *errmsg)  {    perror(errmsg);    exit(1);  }int main(int argc, char **argv)  {    int sockfd;    struct sockaddr_in dstaddr;      if ((sockfd = socket(PF_INET, SOCK_RAW, IPPROTO_ICMP)) == -1)        err_sys("socket");    bzero(&dstaddr, sizeof(dstaddr));    dstaddr.sin_family = AF_INET;    dstaddr.sin_port = htons(0);    if (inet_pton(AF_INET, argv[1], &dstaddr.sin_addr) <= 0)        err_sys("inet_pton");    send_echo_req(sockfd, &dstaddr);    recv_echo_reply(sockfd);    exit(0);  }  void send_echo_req(int sockfd, struct sockaddr_in *dstaddr)  {    char buf[100];    size_t len = sizeof(struct icmp);    struct icmp *icmp;    socklen_t dstlen = sizeof(struct sockaddr_in);    bzero(buf, sizeof(buf));    icmp = (struct icmp *)buf;    icmp->icmp_type = ICMP_ECHO;//8    icmp->icmp_code = 0;    icmp->icmp_id = getpid();    icmp->icmp_seq = 1;    icmp->icmp_cksum = in_cksum((uint16_t *) icmp, sizeof(struct icmp));    if (sendto(sockfd, buf, len, 0, (struct sockaddr *)dstaddr, dstlen) == -1)        err_sys("sendto");  }void recv_echo_reply(int sockfd)  {    char buf[100];    ssize_t n;    struct ip *ip;    struct icmp *icmp;    while (1) {        alarm(5); /* set timeout */        if ((n = read(sockfd, buf, sizeof(buf))) == -1)            err_sys("read");        ip = (struct ip *)buf;        if (ip->ip_p != IPPROTO_ICMP) {            fprintf(stderr, "protocol error.");            exit(1);        }        icmp = (struct icmp *)(buf + sizeof(struct ip));        if (icmp->icmp_type == ICMP_ECHOREPLY) {            if (icmp->icmp_id != getpid()) {                fprintf(stderr, "not this process.");                exit(1);            } else {                printf("destination host is alive.\n");                break;            }        }    }  }uint16_t in_cksum(uint16_t *addr, int len)  {    int nleft = len;    uint32_t sum = 0;    uint16_t *w = addr;    uint16_t answer = 0;    while (nleft > 1) {        sum += *w++;        nleft -= 2;    }      if (nleft == 1) {        *(unsigned char *)(&answer) = *(unsigned char *)w ;        sum += answer;    }    sum = (sum >> 16) + (sum & 0xffff);    sum += (sum >> 16);    answer = ~sum;    return(answer);  }