嵌入式Linux，4G模组使用，命令，EC20、EC25...

嵌入式Linux开发中，移远4G模组通过ppp拨号上网，命令操作过程如下。

chat：调制解调器的自动对话脚本，Chat程序定义了一个计算机和调制解调器之间对话交流，其主要目的是用来在本地PPPD和远端PPPD程序之间建立连接（简单说就是与4G模块进行AT命令交互的流程表，最终实现与ISP运营商的连接）。

pppd：点对点协议守护进程，其功能为实现ppp策略性的内容，包括所有鉴权、压缩/解压和加密/解密等扩展功能的控制协议。

pppdump：将使用pppd记录选项编写的文件转换为人类可读的格式。

pppstats：显示PPP连线状态。pppstats(point to point protocol status)。

一、Test AT Function。

方法一：

root@ms:~# ls /dev/ttyU*
/dev/ttyUSB0  /dev/ttyUSB1  /dev/ttyUSB2  /dev/ttyUSB3  /dev/ttyUSB4
root@ms:~#
root@ms:~# cat /dev/ttyUSB2 &
[1] 1292
root@ms:~# echo -en "AT\r\n" > /dev/ttyUSB2
root@ms:~# ATOKATOKroot@ms:~#

方法二（本人测试没反应）：

root@ms:~# busybox microcom /dev/ttyUSB2

二、Test PPP Function。

1、关闭其它网络，eth和wlan。不关闭，需手动更改默认路由。

root@ms:~# ifconfig eth0 down
root@ms:~#
root@ms:~# ifconfig
lo        Link encap:Local Loopbackinet addr:127.0.0.1  Mask:255.0.0.0inet6 addr: ::1/128 Scope:HostUP LOOPBACK RUNNING  MTU:16436  Metric:1RX packets:4 errors:0 dropped:0 overruns:0 frame:0TX packets:4 errors:0 dropped:0 overruns:0 carrier:0collisions:0 txqueuelen:0RX bytes:312 (312.0 B)  TX bytes:312 (312.0 B)root@ms:~#

root@ms:~# route add defatult 0.0.0.0 mask 255.255.255.255 10.64.64.64
route: resolving defatult
root@ms:~#

2、所需文件。移远EC20、EC25的Modem path为/dev/ttyUSB3。

必须文件：wcdma、wcdma-chat-connect、wcdma-chat-disconnect，目录为/etc/ppp/peers/。

不必须文件：ip-up、ip-down，目录为/etc/ppp。可从Ubuntu系统中拷贝。

/etc/ppp/ip-up、/etc/ppp/ip-down这两个文件分别在ppp链路成功、链接断开时执行一次。可以利用这个去实现pppoe断线自动重连。

3、启动ppp服务。

root@ms:~# pppd call wcdma &
[1] 1288
root@ms:~# pppd options in effect:
debug           # (from /etc/ppp/peers/wcdma)
nodetach                # (from /etc/ppp/peers/wcdma)
dump            # (from /etc/ppp/peers/wcdma)
noauth          # (from /etc/ppp/peers/wcdma)
user password           # (from /etc/ppp/peers/wcdma)
remotename 3gppp                # (from /etc/ppp/peers/wcdma)
/dev/ttyUSB3            # (from /etc/ppp/peers/wcdma)
115200          # (from /etc/ppp/peers/wcdma)
lock            # (from /etc/ppp/peers/wcdma)
connect /usr/sbin/chat -s -v -f /etc/ppp/peers/wcdma-chat-connect               # (from /etc/ppp/peers/wcdma)
disconnect /usr/sbin/chat -s -v -f /etc/ppp/peers/wcdma-chat-disconnect         # (from /etc/ppp/peers/wcdma)
crtscts         # (from /etc/ppp/peers/wcdma)
local           # (from /etc/ppp/peers/wcdma)
hide-password           # (from /etc/ppp/peers/wcdma)
novj            # (from /etc/ppp/peers/wcdma)
novjccomp               # (from /etc/ppp/peers/wcdma)
ipcp-accept-local               # (from /etc/ppp/peers/wcdma)
ipcp-accept-remote              # (from /etc/ppp/peers/wcdma)
ipparam 3gppp           # (from /etc/ppp/peers/wcdma)
noipdefault             # (from /etc/ppp/peers/wcdma)
defaultroute            # (from /etc/ppp/peers/wcdma)
usepeerdns              # (from /etc/ppp/peers/wcdma)
noccp           # (from /etc/ppp/peers/wcdma)
abort on (BUSY)
abort on (NO CARRIER)
abort on (NO DIALTONE)
abort on (ERROR)
abort on (NO ANSWER)
timeout set to 120 seconds
send (AT^M)
expect (OK)
AT^M^M
OK-- got itsend (^MATZ^M)
expect (OK)
^M
ATZ^M^M
OK-- got itsend (^MAT+CGDCONT=1,"IP","3gnet",,0,0^M)
expect (OK)
^M
AT+CGDCONT=1,"IP","3gnet",,0,0^M^M
OK-- got itsend (ATDT*99#^M)
expect (CONNECT)
^M
ATDT*99#^M^M
CONNECT-- got itsend (\d)
Script /usr/sbin/chat -s -v -f /etc/ppp/peers/wcdma-chat-connect finished (pid 1289), status = 0x0
Serial connection established.
using channel 1
Using interface ppp0
Connect: ppp0 <--> /dev/ttyUSB3
Warning - secret file /etc/ppp/pap-secrets has world and/or group access
sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0x4794f369> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x0 <asyncmap 0x0> <auth chap MD5> <magic 0xac3f292c> <pcomp> <accomp>]
No auth is possible
sent [LCP ConfRej id=0x0 <auth chap MD5>]
rcvd [LCP ConfAck id=0x1 <asyncmap 0x0> <magic 0x4794f369> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0xac3f292c> <pcomp> <accomp>]
sent [LCP ConfAck id=0x1 <asyncmap 0x0> <magic 0xac3f292c> <pcomp> <accomp>]
sent [IPCP ConfReq id=0x1 <addr 0.0.0.0> <ms-dns1 0.0.0.0> <ms-dns2 0.0.0.0>]
rcvd [LCP DiscReq id=0x2 magic=0xac3f292c]
rcvd [IPCP ConfReq id=0x0]
sent [IPCP ConfNak id=0x0 <addr 0.0.0.0>]
rcvd [IPCP ConfNak id=0x1 <addr 10.221.137.224> <ms-dns1 61.156.60.66> <ms-dns2 202.102.128.68>]
sent [IPCP ConfReq id=0x2 <addr 10.221.137.224> <ms-dns1 61.156.60.66> <ms-dns2 202.102.128.68>]
rcvd [IPCP ConfReq id=0x1]
sent [IPCP ConfAck id=0x1]
rcvd [IPCP ConfAck id=0x2 <addr 10.221.137.224> <ms-dns1 61.156.60.66> <ms-dns2 202.102.128.68>]
Could not determine remote IP address: defaulting to 10.64.64.64
local  IP address 10.221.137.224
remote IP address 10.64.64.64
primary   DNS address 61.156.60.66
secondary DNS address 202.102.128.68
Script /etc/ppp/ip-up started (pid 1295)
Script /etc/ppp/ip-up finished (pid 1295), status = 0x0root@ms:~#

4、检查IP/DNS/Route。

root@ms:~# ifconfig ppp0
ppp0      Link encap:Point-to-Point Protocolinet addr:10.221.137.224  P-t-P:10.64.64.64  Mask:255.255.255.255UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1RX packets:4 errors:0 dropped:0 overruns:0 frame:0TX packets:4 errors:0 dropped:0 overruns:0 carrier:0collisions:0 txqueuelen:3RX bytes:52 (52.0 B)  TX bytes:58 (58.0 B)root@ms:~#
root@ms:~# cat /etc/resolv.conf
meserver 61.132.163.68
nameserver 202.102.213.68root@ms:~#
root@ms:~# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         0.0.0.0         0.0.0.0         U     0      0        0 ppp0
10.64.64.64     0.0.0.0         255.255.255.255 UH    0      0        0 ppp0
root@ms:~#
root@ms:~# ping www.baidu.com
PING www.baidu.com (14.215.177.38): 56 data bytes
64 bytes from 14.215.177.38: seq=0 ttl=50 time=55.281 ms
64 bytes from 14.215.177.38: seq=1 ttl=50 time=58.692 ms
64 bytes from 14.215.177.38: seq=2 ttl=50 time=60.334 ms
^C
--- www.baidu.com ping statistics ---
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max = 55.281/58.102/60.334 ms
root@ms:~#

5、关闭PPP call。

root@ms:~# killall pppd
Terminating on signal 15
Connect time 3.0 minutes.
Sent 488 bytes, received 971 bytes.
Script /etc/ppp/ip-down started (pid 1305)
sent [LCP TermReq id=0x2 "User request"]
rcvd [LCP TermAck id=0x2]
Connection terminated.
root@ms:~# abort on (ERROR)
abort on (NO DIALTONE)
\send (\k"^M)
send (+++ATH"^M)Good bay
Script /usr/sbin/chat -s -v -f /etc/ppp/peers/wcdma-chat-disconnect finished (pid 1307), status = 0x0
Serial link disconnected.
Script /etc/ppp/ip-down finished (pid 1305), status = 0x0[1]+  Done(5)                 pppd call wcdma
root@ms:~#

6、查看网络节点。

root@ms:~# ifconfig
lo        Link encap:Local Loopbackinet addr:127.0.0.1  Mask:255.0.0.0inet6 addr: ::1/128 Scope:HostUP LOOPBACK RUNNING  MTU:16436  Metric:1RX packets:0 errors:0 dropped:0 overruns:0 frame:0TX packets:0 errors:0 dropped:0 overruns:0 carrier:0collisions:0 txqueuelen:0RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)root@ms:~#

附：

1、指定网络节点ping命令：ping -I ppp0 www.baidu.com。

2、在拨号之前已经启用了以太网eth0，ping广域网失败，原因有两个，一个是路由表中的默认值为eth0生成的，另一个是默认dn服务器地址不能被ppp0识别。

3、默认网关解决如下。

在pppd脚本中使能了defaultroute后，pppd会在拨号成功后向路由表中添加一条默认网关信息，但是因为之前已经有一条默认网关了，于是添加失败，默认网关依然是之前eth设置的，因此在pppd call gprs之前我们应该先route del default来删除默认路由（最好写个脚本来实现删除默认路由–拨号等一系列操作）。

　　或者将ppp0设置为默认路由。

　　先删除原来路由，route del default

　　再将ppp0设置为默认路由，route add default dev ppp0

4、dns问题解决如下。

在pppd脚本中使能了usepeerdns后，pppd会在拨号成功后，在/etc/ppp下生成resolv.conf，这是ISP运营商提供的dns，我们应该将拷贝或者连接到/etc目录下，当然这件事就可以交给ip-up来做。

按照ppp拨号过程中打印信息可以发现，在退出pppd进程时，会调用/etc/ppp/ip-down。因此删除默认网关，恢复dns就交由ip-down脚本做了。

ip-up脚本：

#!/bin/bash
#ip-up
dns_file="/etc/resolv.conf"rm "$dns_file"
ln /etc/ppp/resolv.conf "$dns_file"

ip-down脚本

#!/bin/bash
#ip-down
#set -vx
dns_file="/etc/resolv.conf"rm $dns_filecat > "$dns_file" <<EOF
# auto create by ip-down
nameserver 114.114.114.114
nameserver 8.8.8.8
EOFchmod 755 "$dns_file"/etc/init.d/networking restartecho "Set dns for eth0"

5、设置了断线重拨（lcp-echo-failure、lcp-echo-interval）。