TCP与UDP的区别

具体编程时的区别

部分满足以下几点要求时，应该采用UDP 面向数据报方式

面向连接的TCP的流方式

服务器程序流程（多进程）：

客户端程序流程：

服务器代码

#include <stdio.h>

#include <stdlib.h>

#include <errno.h>

#include <string.h>

#include <sys/types.h>

#include <netinet/in.h>

#include <sys/socket.h>

#include <sys/wait.h>

#define MYPORT 3490

#define BACKLOG 10

void main() {

int sockfd, new_fd;

struct sockaddr_in sa;   //本机地址

struct sockaddr_in their_addr;//远程地址

int sin_size;

if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {

perror("socket");

exit(1);

}

sa.sin_family = AF_INET;

sa.sin_port = htons(MYPORT);

sa.sin_addr.s_addr = INADDR_ANY;

bzero(&(sa.sin_zero), 8);

if (bind(sockfd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {

perror("bind");

exit(1);

}

if (listen(sockfd, BACKLOG) == -1) {

perror("listen");

exit(1);

}

while(1) {

sin_size = sizeof(struct sockaddr_in);

new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size))

if (new_fd == -1) {

perror("accept");

continue;

}

printf(”Got connection from %sn", inet_ntoa(their_addr.sin_addr));

if (fork() == 0) {

if (send(new_fd, "Hello, world! n", 14, 0) == -1)

perror("send");

close(new_fd);

exit(0);

}

close(new_fd);

while(waitpid(-1,NULL,WNOHANG) > 0);

}

}

客户端代码

#include <stdio.h>

#include <stdlib.h>

#include <errno.h>

#include <string.h>

#include <netdb.h>

#include <sys/types.h>

#include <netinet/in.h>

#include <sys/socket.h>

#define PORT 3490

#define MAXDATASIZE 100

int main(int argc, char *argv[])

{

int sockfd, numbytes;

char buf[MAXDATASIZE];

struct hostent *he;

struct sockaddr_in their_addr;//服务器地址

if (argc != 2) {

fprintf(stderr,"usage: client hostnamen");

exit(1);

}

if ((he=gethostbyname(argv[1])) == NULL) {

herror("gethostbyname");

exit(1);

}

if ((sockfd=socket(AF_INET,SOCK_STREAM,0))==-1) {

perror("socket");

exit(1);

}

their_addr.sin_family = AF_INET;

their_addr.sin_port = htons(PORT);

their_addr.sin_addr = *((struct in_addr *)he->h_addr);

bzero(&(their_addr.sin_zero), 8);

if (connect(sockfd, (struct sockaddr *)&their_addr, sizeof(struct sockaddr)) == -1) {

perror("connect");

exit(1);

}

if ((numbytes=recv(sockfd,buf,MAXDATASIZE,0))==-1) {

perror("recv");

exit(1);

}

buf[numbytes] = '';

printf("Received: %s",buf);

close(sockfd);

return 0;

}

服务器程序流程（单进程）：

客户端程序流程：

UDP方式下服务器与客户端程序差别不大，仅第三步不同。

服务器

#include <stdio.h>

#include <stdlib.h>

#include <errno.h>

#include <string.h>

#include <sys/types.h>

#include <netinet/in.h>

#include <sys/socket.h>

#include <sys/wait.h>

#define MYPORT 3490

void main()

{

int sockfd;

struct sockaddr_in my_addr;

struct sockaddr_in their_addr;

int sin_size, retval;

char buf[128];

if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {

perror("socket");

exit(1);

}

my_addr.sin_family = AF_INET;

my_addr.sin_port = htons(MYPORT);

my_addr.sin_addr.s_addr = INADDR_ANY;

bzero(&(my_addr.sin_zero), 8);

if (bind(sockfd, (struct sockaddr *)&my_addr, sizeof(my_addr)) == -1) {

perror("bind");

exit(1);

}

while(1) {

retval = recvfrom(sockfd, buf, 128, 0, (struct sockaddr *)&their_addr, &sin_size);//获取远程主机的报文，并解析

printf("Received datagram from %sn",inet_ntoa(their_addr.sin_addr));

if (retval == 0) {

perror (“recvfrom");

close(sockfd);

break;

}

retval = sendto(sockfd, buf, 128, 0, (struct sockaddr *)&their_addr, sin_size);

}

}

客户端

#include <stdio.h>

#include <stdlib.h>

#include <errno.h>

#include <string.h>

#include <netdb.h>

#include <sys/types.h>

#include <netinet/in.h>

#include <sys/socket.h>

#define PORT 3490

#define MAXDATASIZE 100

int main(int argc, char *argv[])

{

int sockfd, numbytes, sin_size;

char buf[MAXDATASIZE] = “Hello, world!”;

struct hostent *he; //

struct sockaddr_in their_addr;//服务器地址

if (argc != 2) {

fprintf(stderr,"usage: client hostnamen");

exit(1);

}

if ((he=gethostbyname(argv[1])) == NULL) {

herror("gethostbyname");

exit(1);

}

if ((sockfd=socket(AF_INET,SOCK_DGRAM,0))==-1) {

perror("socket");

exit(1);

}

their_addr.sin_family = AF_INET;

their_addr.sin_port = htons(PORT);

their_addr.sin_addr = *((struct in_addr *)he->h_addr);

bzero(&(their_addr.sin_zero), 8);

numbytes = sendto(sockfd, buf, MAXDATASIZE, 0, (struct sockaddr *)&their_addr,sizeof(their_addr))；//向服务器发送任一报文

if (numbytes == -1) {

perror(“sendto");

exit(1);

}

printf(“Send: %s",buf);

numbytes = recvfrom(sockfd, buf, MAXDATASIZE, 0, (struct sockaddr *)&their_addr, &sin_size);

if (numbytes == -1) {

perror("recvfrom");

exit(1);

}

buf[numbytes] = '';

printf("Received: %s",buf);

close(sockfd);

return 0;

}