TCP 编程
涉及函数
函数定义在 sys/socket.h,相关数据类型定义在 sys/types.h。
客户端 服务端
socket socket
bind
listen
accept
connect
send/recv send/recv
close close
程序流图
UDP 编程
涉及函数
函数定义在 sys/socket.h,相关数据类型定义在 sys/types.h。
客户端 服务端
socket socket
bind
sendto/recvfrom recvfrom/sendto
close close
程序流图
编程实例
TCP 服务端
#include <unistd.h>
#include <arpa/inet.h>
#define MAXBUF 1024
// 简单判断一下是否是IPv6地址
inline bool isipv6(const char* ip)
{
return ip? strchr(ip, ':') : false;
}
int main(int argc, char **argv)
{
int sockfd, new_fd;
socklen_t len;
int family = AF_INET;
union {
struct sockaddr sa;
struct sockaddr_in sa4; // IPv4
struct sockaddr_in6 sa6; // IPv6
} myaddr, theiraddr;
unsigned int myport, lisnum;
char buf[MAXBUF + 1];
if (argv[1])
myport = atoi(argv[1]);
else
myport = 8088;
if (argv[2])
lisnum = atoi(argv[2]);
else
lisnum = 2;
if (isipv6(argv[3])) {
family = AF_INET6;
}
if ((sockfd = socket(family, SOCK_STREAM, 0)) == -1) {
perror("socket");
exit(1);
} else
printf("socket created\n");
bzero(&myaddr, sizeof(myaddr));
if (family == AF_INET) { // IPv4
myaddr.sa4.sin_family = AF_INET;
myaddr.sa4.sin_port = htons(myport);
if (argv[3])
inet_pton(AF_INET, argv[3], &myaddr.sa4.sin_addr);
else
myaddr.sa4.sin_addr.s_addr = INADDR_ANY;
} else { // IPv6
myaddr.sa6.sin6_family = AF_INET6;
myaddr.sa6.sin6_port = htons(myport);
if (argv[3])
inet_pton(AF_INET6, argv[3], &myaddr.sa6.sin6_addr);
else
myaddr.sa6.sin6_addr = in6addr_any;
}
if (bind(sockfd, (struct sockaddr *) &myaddr, sizeof(myaddr)) == -1) {
} else
printf("binded\n");
if (listen(sockfd, lisnum) == -1) {
perror("listen");
exit(1);
} else
printf("begin listen\n");
while (1) {
len = sizeof(theiraddr);
if ((new_fd = accept(sockfd, (struct sockaddr *) &theiraddr, &len)) == -1) {
perror("accept");
exit(errno);
} else {
if (theiraddr.sa.sa_family == AF_INET)
printf("server: got connection from %s, port %d, socket %d\n",
inet_ntop(AF_INET, &theiraddr.sa4.sin_addr, buf, sizeof(buf)),
ntohs(theiraddr.sa4.sin_port), new_fd);
else
printf("server: got connection from %s, port %d, socket %d\n",
inet_ntop(AF_INET6, &theiraddr.sa6.sin6_addr, buf, sizeof(buf)),
ntohs(theiraddr.sa6.sin6_port), new_fd);
}
/* 开始处理每个新连接上的数据收发 */
bzero(buf, MAXBUF + 1);
strcpy(buf,
"这是在连接建立成功后向客户端发送的第一个消息\n只能向new_fd这个用accept函数新建立的socket发消息,不>能向sockfd这个监听socket发送消息,监听socket不能用来接收或发送消息");
/* 发消息给客户端 */
len = send(new_fd, buf, strlen(buf), 0);
if (len < 0) {
printf
("消息'%s'发送失败!错误代码是%d,错误信息是'%s'\n",
buf, errno, strerror(errno));
} else
printf("消息'%s'发送成功,共发送了%d个字节!\n",
buf, len);
bzero(buf, MAXBUF + 1);
/* 接收客户端的消息 */
len = recv(new_fd, buf, MAXBUF, 0);
if (len > 0)
printf("接收消息成功:'%s',共%d个字节的数据\n",
buf, len);
else
printf
("消息接收失败!错误代码是%d,错误信息是'%s'\n",
errno, strerror(errno));
/* 处理每个新连接上的数据收发结束 */
}
close(sockfd);
return 0;
}
TCP 客户端
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <sys/socket.h>
#include <resolv.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#define MAXBUF 1024
inline bool isipv6(const char* ip)
{
return ip? strchr(ip, ':') : false;
}
int main(int argc, char **argv)
{
int sockfd, len;
int family = AF_INET;
union {
struct sockaddr sa;
struct sockaddr_in sa4; // IPv4
struct sockaddr_in6 sa6; // IPv6
} dest;
char buffer[MAXBUF + 1];
if (argc != 3) {
printf("参数格式错误!正确用法如下:\n\t\t%s IP地址 端口\n\t比如:\t%s 127.0.0.1 80\n此程序用来从某个 IP 地址的服务器某个端口接收最多 MAXBUF 个字节的消息\n",
argv[0], argv[0]);
exit(0);
}
if (isipv6(argv[1])) {
family = AF_INET6;
}
/* 创建一个 socket 用于 tcp 通信 */
if ((sockfd = socket(family, SOCK_STREAM, 0)) < 0) {
perror("Socket");
exit(errno);
}
printf("socket created\n");
/* 初始化服务器端(对方)的地址和端口信息 */
bzero(&dest, sizeof(dest));
if (family == AF_INET) { // IPv4
dest.sa4.sin_family = AF_INET;
dest.sa4.sin_port = htons(atoi(argv[2]));
inet_pton(AF_INET, argv[1], &dest.sa4.sin_addr);
} else { // IPv6
dest.sa6.sin6_family = AF_INET6;
dest.sa6.sin6_port = htons(atoi(argv[2]));
inet_pton(AF_INET6, argv[1], &dest.sa6.sin6_addr);
}
printf("address created\n");
/* 连接服务器 */
if (connect(sockfd, (struct sockaddr *) &dest, sizeof(dest)) != 0) {
perror("Connect ");
exit(errno);
}
printf("server connected\n");
/* 接收对方发过来的消息,最多接收 MAXBUF 个字节 */
bzero(buffer, MAXBUF + 1);
/* 接收服务器来的消息 */
len = recv(sockfd, buffer, MAXBUF, 0);
if (len > 0)
printf("接收消息成功:'%s',共%d个字节的数据\n",
buffer, len);
else
printf
("消息接收失败!错误代码是%d,错误信息是'%s'\n",
errno, strerror(errno));
bzero(buffer, MAXBUF + 1);
strcpy(buffer, "这是客户端发给服务器端的消息");
/* 发消息给服务器 */
len = send(sockfd, buffer, strlen(buffer), 0);
if (len < 0)
printf
("消息'%s'发送失败!错误代码是%d,错误信息是'%s'\n",
buffer, errno, strerror(errno));
else
printf("消息'%s'发送成功,共发送了%d个字节!\n",
buffer, len);
/* 关闭连接 */
close(sockfd);
return 0;
}
UDP 服务端
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <string.h>
#define LOCALPORT 8088
#define MAXBUF 1024
inline bool isipv6(const char* ip)
{
return ip? strchr(ip, ':') : false;
}
int main(int argc,char *argv[])
{
int mysocket, len;
int i=0;
int family = AF_INET;
union {
struct sockaddr sa;
struct sockaddr_in sa4;
struct sockaddr_in6 sa6;
} addr, theiraddr;
int addr_len;
char msg[MAXBUF];
char buf[INET6_ADDRSTRLEN];
char* myip = NULL;
int myport = LOCALPORT;
if (argc > 1)
myport = atoi(argv[1]);
if (argc > 2)
myip = argv[2];
if (isipv6(myip))
family = AF_INET6;
if((mysocket = socket(family, SOCK_DGRAM, 0)) < 0) {
perror("error");
return(1);
} else {
printf("socket created ...\n");
printf("socket id: %d \n",mysocket);
}
bzero(&addr, sizeof(addr));
if (family == AF_INET) { // IPv4
addr.sa4.sin_family = AF_INET;
addr.sa4.sin_port = htons(myport);
if (myip)
inet_pton(AF_INET, myip, &addr.sa4.sin_addr);
else
addr.sa4.sin_addr.s_addr = INADDR_ANY;
} else { // IPv6
addr.sa6.sin6_family = AF_INET6;
addr.sa6.sin6_port = htons(myport);
if (myip)
inet_pton(AF_INET6, myip, &addr.sa6.sin6_addr);
else
addr.sa6.sin6_addr = in6addr_any;
}
if(bind(mysocket, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
perror("connect");
exit(1);
} else {
printf("bink ok.\n");
printf("local port: %d\n", myport);
}
while(1) {
addr_len = sizeof(theiraddr);
bzero(&addr, sizeof(theiraddr));
bzero(msg, sizeof(msg));
len = recvfrom(mysocket, msg, sizeof(msg), 0, (struct sockaddr *)&theiraddr, (socklen_t*)&addr_len);
printf("%d:", i);
i++;
if (theiraddr.sa.sa_family == AF_INET) { // IPv4
inet_ntop(AF_INET,&theiraddr.sa4.sin_addr,buf,sizeof(buf));
} else { // IPv6
inet_ntop(AF_INET6,&theiraddr.sa6.sin6_addr,buf,sizeof(buf));
}
printf("message from ip %s, ", buf);
printf("Received message: %s\n", msg);
if(sendto(mysocket, msg, len, 0, (struct sockaddr *)&theiraddr, addr_len)<0) {
printf("error");
exit(1);
}
}
/* 关闭连接 */
close(mysocket);
return 0;
}
UDP 客户端
#include <stdio.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <sys/socket.h>
#include <string.h>
#define REMOTEPORT 8088
#define REMOTEIP "127.0.0.1"
#define MAXBUF 1024
inline bool isipv6(const char* ip)
{
return ip? strchr(ip, ':') : false;
}
int main(int argc,char *argv[])
{
int mysocket,len;
int i=0;
int family = AF_INET;
union {
struct sockaddr sa;
struct sockaddr_in sa4;
struct sockaddr_in6 sa6;
} addr;
int addr_len;
char msg[MAXBUF];
char* remoteip = (char*)REMOTEIP;
int remoteport = REMOTEPORT;
if (argc > 1)
remoteport = atoi(argv[1]);
if (argc > 2)
remoteip = argv[2];
if (isipv6(remoteip))
family = AF_INET6;
if((mysocket = socket(family, SOCK_DGRAM, 0)) < 0) {
perror("error");
exit(1);
} else {
printf("socket created ...\n");
printf("socket id: %d \n", mysocket);
printf("rmote ip: %s \n", remoteip);
printf("remote port: %d \n", remoteport);
}
addr_len = sizeof(addr);
bzero(&addr, sizeof(addr));
if (family == AF_INET) { // IPv4
addr.sa4.sin_family = AF_INET;
addr.sa4.sin_port = htons(remoteport);
inet_pton(AF_INET, remoteip, &addr.sa4.sin_addr);
} else { // IPv6
addr.sa6.sin6_family = AF_INET6;
addr.sa6.sin6_port = htons(remoteport);
inet_pton(AF_INET6, remoteip, &addr.sa6.sin6_addr);
}
while(1) {
bzero(msg, sizeof(msg));
len = read(STDIN_FILENO, msg, sizeof(msg));
if(sendto(mysocket, msg, sizeof(msg), 0, (struct sockaddr *)&addr, addr_len) < 0) {
perror("error");
exit(1);
}
bzero(msg, sizeof(msg));
len = recvfrom(mysocket, msg, sizeof(msg), 0, (struct sockaddr *)&addr, (socklen_t*)&addr_len);
printf("%d: ", i);
i++;
printf("Received message: %s\n", msg);
}
/* 关闭连接 */
close(mysocket);
return 0;
}
参考
[1] https://www.cnblogs.com/wuyuxuan/p/5541598.html
[2] https://blog.csdn.net/qq_26437925/article/details/51892362